Aryna Sabalenka had won 18 straight matches at the US Open going into Thursday, and on Wednesday her hold on the No. 1 ranking ended anyway. Elena Rybakina's quarterfinal win over Qinwen Zheng secured the top spot for Rybakina whatever happens in New York this week; the list that published on Monday, September 14, closed Sabalenka's run at 99 weeks. What came next was Jessica Pegula, on Thursday night at Arthur Ashe Stadium, for the third US Open in a row. As of September 9, 2026, at 3:08 p.m. ET, when this page was written, Kalshi's match market had Sabalenka at 63¢ bid, 64¢ ask, and Pegula at 36¢ bid, 37¢ ask. Read as a probability, the two-time defending champion was a 63 to 64 percent favorite. On the same exchange's tournament board, Sabalenka was 36¢ to 37¢ to win the whole thing and Pegula was 12¢ to 13¢. The match has been played: Sabalenka won 7-5, 6-2 in 1 hour and 20 minutes on Thursday, September 10, the match market closed at 8:39 p.m. ET and paid her contract $1.00 a minute later, and the title board finalized two days after that on a name that was on neither side of this net. Every market on this page was re-pulled on September 16, 2026, for its settlement and lifetime volume; the quotes and order-book depth below stand as the September 9 pre-match record, and the section after the board carries what the tape did between that pull and the payout.
A third of the semifinal, an eighth of the title. The question this page exists to answer is whether the space between those two numbers is where the value is, and my read before the evidence was that it was not, because the gap was a second match with a name already attached to it. The head-to-head is where the argument about the first match lives, and the head-to-head's most recent entry going into Thursday, the set the title refers to, was a 6-0 third set that Pegula won; the most recent entry now is Thursday's 6-2. The order book was where the argument ended, and it ended with 233,614 contracts of Pegula sitting for sale at the 37¢ ask and just above it. I will get to who was offering them.
How Sabalenka And Pegula Got To Thursday
Both women needed three sets on Tuesday, and both spent part of the day behind. Two escapes is the form the market spent Wednesday pricing at 63¢ to 64¢, so the escapes are worth a close look.
Sabalenka beat Linda Noskova 7-6(1), 3-6, 7-6(7) in 2 hours and 22 minutes, from 2-4 down in the third set, and finished the match tiebreak with a second-serve ace. Noskova is this year's Wimbledon champion, which made it a meeting of two reigning major champions, and it went to the last few points. The WTA's report counts it as her sixth consecutive US Open semifinal, her 15th at a Grand Slam, her first three-set win at a major this year, and her first win over a top-10 player since the Miami final in March. Noskova hit 46 winners and 18 aces and saved seven of nine break points, and still lost. "I feel like I got lucky," Sabalenka said afterward. On the numbers, she did, and the market agreed in real time: at 1:30 p.m., with Sabalenka a break down in the third set, her contract to win the whole tournament printed at 9¢ and 10¢, and by the 2 p.m. hour, match won, it was back near 40¢.
Pegula's night ran later and looked worse before it looked better. Navarro took the first set 6-3 and broke for 2-1 in the third before Pegula won four straight games to close out 3-6, 6-4, 6-3, her second comeback from a set down in this tournament after the Leylah Fernandez match in the third round. ESPN puts her three-set wins for the season at 19, the most on the women's tour. The Sports Encounter's box score has her winning 111 points to 102, converting five of 12 break points to Navarro's four of 12, and hitting eight double faults. Her own title contract had its evening in the same order: a run of sells at 10:21 p.m. printed it as low as 3¢ late in the match, and it closed the night at 13¢ to 14¢. The page I wrote on that quarterfinal argued the 78-cent price on her was a head-to-head price; the head-to-head is now 5-0.
Then Wednesday changed the shape of the whole draw. Rybakina came back to beat Zheng 3-6, 6-1, 6-4 for her first US Open semifinal and the top ranking, and in the last quarterfinal, still in progress when this page was written, Mirra Andreeva took the first set 6-2 from Coco Gauff, with Kalshi's in-play market on that match at 63¢ to 64¢ on Andreeva. Gauff saved two match points and won it 2-6, 7-6(7), 6-2, and the winner played Rybakina. Sabalenka and Pegula played each other in the night session, which opened at 7 p.m. ET.
Three US Opens, 13 Matches, One 6-0 Set
Sabalenka and Pegula had met 13 times on tour going into Thursday and Sabalenka led 9-4, including both previous US Open meetings; the WTA's count after the semifinal is 10-4. ESPN notes they are the fourth women's pair in the Open era to meet in the semifinals or later at three consecutive US Opens. The two New York matches are the ones the price was built on, so they deserve their own paragraphs.
The 2024 final went 7-5, 7-5 to Sabalenka in 1 hour and 53 minutes under a closed roof. The scoreline undersells how close it was. Sabalenka failed to serve out the first set at 5-4, needed a 14-point hold to reach 6-5, and took the set on her fifth set point. In the second, Pegula came from 0-3 down to lead 5-4 and served for the set; Sabalenka broke, held, and closed it. The WTA's stat line is 40 winners to 17 and 18 of 23 points won at the net. A year later the 2025 semifinal went 4-6, 6-3, 6-4 the same way. Pegula took the first set from 2-4 down, then created four break points, three of them in the third set, and converted none. "I don't know how I didn't break back," she said. Sabalenka hit 43 winners.
Two matches, five sets, and Pegula was a hold or a break point from turning either of them. The price on Thursday was the market's estimate of whether the third one would go the same way, and the freshest evidence said the pattern could break. In the Berlin semifinal on June 20, on grass, Pegula won 6-4, 6-7(4), 6-0, with a two-hour rain delay in the second-set tiebreak that cost her a 3-1 lead in it. She came back out and won 20 of the last 27 points. The WTA's report notes their previous three meetings had all gone three sets; this one did too, and ended with a set Sabalenka did not win a game in. They had not played since.
That was the case a 36-cent buyer was making: the last two here were closer than the scores, the last one anywhere was a rout the other way, and Sabalenka, the one being asked to win a third straight one here, needed a 10-7 match tiebreak to get past Noskova. Before weighing it, it helps to see what the crowd had already decided.
What Kalshi Is Pricing, And How The Price Got Here
On Kalshi, each woman is her own yes-or-no contract under the event ticker KXWTAMATCH-26SEP10SABPEG, paying $1.00 if she wins the semifinal and nothing if she does not, with the price in cents standing in for probability; the plain-English guide to prediction markets covers the mechanics and the guide to betting sports on Kalshi covers placing an order. The market's rules mattered for a Thursday-night match, so one sentence on them: a pre-match withdrawal resolves the contract to a fair price under Kalshi's rules, while a retirement after a ball has been played pays the woman who advances.
The market listed at 10:55 p.m. ET Tuesday, and the first print on the Sabalenka side, 14 contracts at 10:58 p.m., went through at 71¢. It did not hold. Within 10 minutes the price was 62¢, and at 11:19 p.m. it printed 59¢, the lowest it had been to that point. Then the buying started, a cent or two an hour through the night, and in the 4 a.m. hour alone 7,006 contracts went through at 64¢, including a single 3,505-contract fill at 4:18 a.m. From there to the pull the price traded between 63¢ and 65¢ with 64¢ on nearly every fill, the one print of size away from it a 1,246-contract buy at 65¢ just after 3 p.m. Of the 32,716 contracts traded on the Sabalenka leg, 32,237 were buyers lifting the offer, 98.5 percent, at a volume-weighted average of 63.6¢.
The Pegula leg tells a quieter story. It opened at 43¢ at 11:12 p.m., slid to 41¢ just after midnight and 38¢ before 2 a.m., and had printed 37¢ in every hour from 10 a.m. to the pull, with a handful of fills at 36¢ after 2 p.m. and a 36¢ bid under it that was four contracts deep. Its biggest single fill was a seller, not a buyer: 2,126 contracts of Pegula sold at 39¢ at 1:25 a.m. Wednesday, the same second a 1,649-contract buy of Sabalenka went through at 60¢ on the other leg. Somebody took the same view on both legs at once. Buyers account for 4,478 of the 7,196 contracts traded on her side, 62 percent, against the 98.5 percent on Sabalenka's.
With the price history in hand, here is the board as it stood at 3:08 p.m. ET Wednesday, the semifinal legs beside the tournament board that gives the second half of this page its argument, with how each contract settled and what it traded in its life added from the September 16 re-pull.
| Market (Kalshi Event) | Contract | Bid, Sept 9 | Ask, Sept 9 | Traded by the Sept 9 pull | Traded, lifetime | Settled |
|---|---|---|---|---|---|---|
| Sabalenka Vs Pegula, Semifinal (Thu. Sept 10) | Aryna Sabalenka wins | 63¢ | 64¢ | 32,716 | 5,351,356 | Yes, $1.00, 8:40 p.m. ET Sept 10 |
| Sabalenka Vs Pegula, Semifinal (Thu. Sept 10) | Jessica Pegula wins | 36¢ | 37¢ | 7,196 | 5,480,028 | No, 8:40 p.m. ET Sept 10 |
| US Open Women's Champion (KXWTA-26USO) | Aryna Sabalenka | 36¢ | 37¢ | 552,514 | 1,208,930 | No, 6:43 p.m. ET Sept 12 |
| US Open Women's Champion (KXWTA-26USO) | Elena Rybakina | 25¢ | 27¢ | 477,891 | 1,085,403 | Yes, $1.00, 6:43 p.m. ET Sept 12 |
| US Open Women's Champion (KXWTA-26USO) | Jessica Pegula | 12¢ | 13¢ | 399,203 | 467,441 | No, 9:06 p.m. ET Sept 10 |
| US Open Women's Champion (KXWTA-26USO) | Mirra Andreeva | 12¢ | 13¢ | 316,495 | 346,221 | No, 5:16 p.m. ET Sept 9 |
| US Open Women's Champion (KXWTA-26USO) | Coco Gauff | 11¢ | 14¢ | 800,810 | 1,100,827 | No, 11:36 p.m. ET Sept 10 |
Bid and ask are the quotes on each yes contract as of September 9, 2026, at 3:08 p.m. ET, from the pull this page was written on. The two traded columns are that pull's lifetime count and the finalized lifetime count from a re-pull of the same Kalshi public market data on September 16, 2026, at about 3:35 p.m. ET, with each contract's settlement time in ET. Gauff and Andreeva were mid-match at the first pull, which is why Gauff's quote was three cents wide. The five title midpoints at the pull summed to 100. Open interest at settlement was 2,851,025 contracts on the Sabalenka leg of the match and 3,442,360 on the Pegula leg.
What Moved Since September 13
Nothing on the board, because the board is finished: both semifinal contracts, the set-one contracts and all 31 contracts on the title board are finalized, and the September 16 re-pull returned the settlement stamps in the table and nothing that can still trade. What this section carries is the tape between the Wednesday pull and the payout, which the page's last edit on September 13 did not have.
The pre-match part was quiet. From the 3:08 p.m. pull on Wednesday to 7:15 p.m. on Thursday, the Sabalenka leg traded 854,338 contracts between 63¢ and 65¢ and went into the match at 65¢; the Pegula leg traded 688,578 between 35¢ and 37¢ and went in at 36¢. In those 28 hours not one print reached the 38¢ or 39¢ steps of the 233,614-contract wall described further down. The 37¢ rung absorbed everything that came, and nobody paid up for Berlin.
The match part was not quiet. The quarter-hour from 7:15 p.m. took Sabalenka from 64¢ to 75¢ and back to 69¢, and by 7:45 p.m. she had printed as low as 59¢. Then, between 7:46:10 and 7:46:16 p.m., a seller swept her from 59¢ to 52¢ through a crowd that kept buying the dip, the largest fill 3,465 contracts at 52¢, while on the other leg a buyer lifted Pegula from 43¢ to 49¢ in two seconds, one 12,022-contract fill at 43¢ on the way. For a few seconds at 7:46 p.m., 19 minutes before the set-one contract Kalshi also listed on this match closed at 8:05 p.m., the exchange had the match within three cents of a coin flip. It was the only time. Sabalenka printed 80¢ at 7:58 p.m., 90¢ at 8:15, 95¢ at 8:20 and 99¢ at 8:31; Pegula's leg printed 20¢ at 7:58, 10¢ at 8:15, 5¢ at 8:20 and a penny at 8:34. The market closed at 8:39:33 p.m. and settled a minute later. Per the WTA's match report, Sabalenka took the first set by holding for 6-5 from 5-5 and breaking, broke for 3-1 in the second on her fourth break point, faced one break point all match, and reached her fourth straight US Open final; Pegula won five of 19 points on her second serve. "I thought her level was insanely high," Pegula said afterward. "Honestly, I don't really know if there was much I could do today."
The size came late. At 8:33:53 p.m., with Sabalenka at 98¢ and the match minutes from over, one second of tape holds 63 fills and 404,989 contracts, every one of them a taker selling Sabalenka at 98¢, the largest 339,468 contracts: two cents a contract on the chance of a collapse, about $6,800 at risk on that one order for a $339,468 gross payout if it came. In two seconds at 8:36 p.m., three fills on the Pegula leg bought 140,215, 82,630 and 62,546 contracts of her at 1¢, a second after a 77,968-contract fill had sold her at the same price. The Pegula leg finished with 5,480,028 contracts to Sabalenka's 5,351,356, after the Wednesday pull had them at 7,196 to her 32,716 and 7:15 p.m. Thursday had them at 695,774 to 887,054, and 87 percent of Pegula's lifetime volume went through after 7:15 p.m. The volume-weighted average of every in-match Sabalenka fill was 87.1¢; of every in-match Pegula fill, 17.0¢.
The title board priced the final where this page's arithmetic said it would. Sabalenka's title contract went into the match at 38¢, its last print before 7 p.m., printed 46¢ by the end of the 7 p.m. hour and 62¢ in the 8 p.m. hour, and the biggest title-leg print of the night, 8,552 contracts sold at 59¢, went through at 8:39:29 p.m., four seconds before the match market closed. It then sat at 57¢ and 58¢ for the whole of Friday, on 54,224 contracts. Divide the 36.5-cent title midpoint by the 63.5-cent match midpoint, as the section on the gap does below, and you get 57 percent, the market's Wednesday estimate of her beating whoever came out of the other half; with the semifinal won, the board priced her at 57 to 58 for a final against Rybakina, who beat Gauff 3-6, 6-4, 6-4 in the second semifinal. Pegula's title contract printed 15¢ at its high in the 7 p.m. hour, 1¢ at 8:45 p.m., and settled at zero at 9:06 p.m. ET. Rybakina's paid $1.00 at 6:43 p.m. ET on Saturday, September 12, after she beat Sabalenka 6-4, 5-7, 6-2 in the final; Sabalenka's title contract, 60¢ at 3:59 p.m. that afternoon, was 1¢ on its last print at 6:37 p.m. The rankings caught up on Monday, September 14: per Tennis365's rankings roundup, Rybakina to No. 1 on 9,902 points, Sabalenka to No. 2 on 7,875 and Pegula to No. 3 on 7,265, 610 points back, with the WTA's rankings note closing Sabalenka's run at the top at 99 weeks.
Back to the board as it stood on Wednesday, and the row that had barely moved.
More US Open boards, settled: US Open men's title board (Alexander Zverev, 43¢ bid at this page's pull with Ben Shelton at 37¢, won Sunday's final) · US Open women's title board (Elena Rybakina, 25¢ bid, 27¢ ask at the pull, won the title)
The row to sit with was Pegula's title line, because it had barely moved. On Monday evening, with a quarterfinal, a semifinal and a final still between her and the trophy, Kalshi quoted her at 12¢ bid, 13¢ ask. She had since won the quarterfinal, and she was 12¢ bid, 13¢ ask. The price history in between was violent. The 3¢ prints late in her own quarterfinal are described above; the high end came earlier in the day, when a buyer took 3,579 contracts of Pegula's title line at 16¢ at 1:33 p.m., three minutes after Sabalenka's 9¢ and 10¢ prints against Noskova. The market spent Tuesday afternoon pricing a draw without Sabalenka in it and then put her back. Pegula's reward for winning a round was a price that said the two matches she had left were worth exactly what the three were.
The Gap Between A Third And An Eighth
Divide the title price by the match price and you get the market's estimate of each woman's chance of winning the final, given that she gets there. For Pegula, a 12.5-cent midpoint over a 36.5-cent midpoint is about 34 percent. For Sabalenka, 36.5 over 63.5 is about 57 percent; on the asks a buyer actually pays, Pegula's number is 35. So the board was saying that if Pegula beat Sabalenka on Thursday, she was roughly a one-in-three shot on Saturday, and that if Sabalenka won, she was better than even money.
Whether 34 percent was stingy depended entirely on who would be on the other side of the net on Saturday, and the other half of the draw had already told us. The three names left there added up to a 51-cent midpoint on the title board, and Rybakina, the newly minted No. 1, held 26 of it. Rybakina leads Pegula 6-3 and has won five of their last six, including all three meetings this year: the Australian Open semifinal in January, 6-3, 7-6, and quarterfinals at Indian Wells and Miami in March. If Gauff came through instead, she was the woman who beat Pegula 6-2, 6-4 in the Cincinnati final three weeks ago. And if it were Andreeva, the player the in-play market liked at pull time, Pegula had never played her, so a quarter of the bottom half was a matchup with no evidence in it at all. A final-win probability in the mid-30s is what those records look like when a market prices them, and the one name on that side Pegula had not been beaten by lately was the one she had never met. It was the head-to-head against the other side of the draw, and Pegula did not own that one.
So the gap had a name, and the name was mostly Rybakina. That left the semifinal price itself, which is where the argument actually lived. In payout terms, a 37-cent contract turns $37 into $100 if Pegula wins Thursday, and a 13-cent title contract turns $13 into $100 if she wins twice. The title contract is a two-match parlay priced at 37 times 35. A reader who believes Pegula's chance in the final is better than 35 percent should be looking at the title contract, and a reader who believes Pegula's real chance on Thursday is better than 37 percent should be looking at the match contract, and only the second of those readers has the head-to-head on their side.
A Worked Example: What 37¢ Buys, After The Fee
With the exchange's cut included: 100 Pegula contracts at 37¢ cost $37 and pay $100 if she wins Thursday, and Kalshi's published taker fee, 0.07 times contracts times price times one minus price, rounded up to the next cent, takes $1.64 on that order. The fee pushes the break-even from 37 percent to 38.6 percent. The same 100 contracts of Sabalenka at 64¢ cost $64 and pay the same $100, with a $1.62 fee and a break-even of 65.6 percent. The title contract at 13¢ costs $13 for the same $100, with an 80-cent fee and a break-even of 13.8 percent. There is no screen to re-run it against now, since all three contracts are finalized; of the three, only the Sabalenka contract paid, which settles the outcome and not whether 64¢ was the right price.
The sportsbooks give a second opinion in their own units. The moneyline LegalSportsBetting quoted Wednesday was Sabalenka -185, Pegula +155, which implies about 65 percent and 39 percent with the book's margin still inside the numbers; strip the margin and it lands near 62 and 38. On Kalshi you pay the 37¢ ask for Pegula, the book's margin-free number is 37.7, and the fee's break-even of 38.6 sits above both. The edge against the sportsbooks is seven-tenths of a cent before the fee, and the fee eats it.
The Order Book Is Where The Edge Would Have To Be
A price that holds 63¢ to 64¢ through 11 hours of one-way buying has a wall behind it, and Kalshi publishes the wall. At 3:08 p.m. ET the resting offers on the Pegula leg read 50,324 contracts at 37¢, 60,998 at 38¢ and 122,292 at 39¢: the 233,614 contracts I promised at the top, all of them Pegula for sale at the ask or within two cents above it, more than 32 times what her contract had traded up to that point. Getting her price to 40¢ meant buying every one of them. The bid side under her was real too, 20,846 contracts at 35¢ and 33,437 at 34¢, so a seller could not move her much either. On the Sabalenka leg the picture is lopsided in an instructive way: 9,560 contracts bid at 63¢, 42,409 at 62¢ and 32,926 at 61¢ underneath, but only 250 offered at 64¢, which is how a single 1,246-contract buyer pushed a print to 65¢ at 3:03 p.m. The real resistance on her started at 65¢, where 33,821 sat, and 66¢, where 90,074 did.
That was what a stable price looked like on an exchange. Size that deep on both sides of the Pegula leg is usually the signature of market makers quoting a spread rather than one trader with a thesis about Berlin, and the depth of it said that whoever was quoting had no interest in letting a few thousand contracts of enthusiasm move her. The crowd that had bought 32,000 contracts of Sabalenka since Tuesday night had not tried. If there was an edge on Pegula at 37, taking it meant buying into that wall, and the wall had shown its size.
The Case For Pegula At 37, Argued Honestly
The 37 cents may well have been right. What follows is what it would have needed to be wrong about, because the underdog case here was specific.
It starts with the break points. Pegula created four against Sabalenka last September and converted none; she converted five of 12 against Navarro on Tuesday, into a serve that made her save eight of her own. Sabalenka, for her part, created nine break points against Noskova on Tuesday and converted two. The 6-0 set in Berlin was built the same way, 20 of the last 27 points, on a Sabalenka who had just won a tiebreak and should have had the momentum. Pegula's 19 three-set wins this season said she was comfortable in the third hour, and Thursday's match, if the first two here were a guide, would have one.
The counter was everything Sabalenka had done on this court. Eighteen straight wins, two titles, a 2-0 record against Pegula in New York, and, per LegalSportsBetting's count, 10 consecutive tiebreaks won at the US Open, the latest of them Tuesday's match tiebreak after she came back from 2-4 down in the third. The 40 winners to 17 in the 2024 final and the 43 in the 2025 semifinal are the same stat line: when the points get short, she hits through Pegula, and Pegula's flat ball had yet to find an answer on this surface at this event. Berlin was on grass, and the rain did some of the work.
If I had to name the one thing I would watch, it was the first break point Pegula earned, because last September's four went begging and a year of three-set wins said she had been finishing them since. The market's 37¢ already assumed she would play well and lose a close one, the way she had twice. It was not priced for the first one to land. It did not need to be: per the WTA, she earned one all night, and Sabalenka saved it.
Where The Real Question Sits
So the thesis held. The distance between a third of the semifinal and an eighth of the title was a second match against Rybakina, or against the woman who beat Pegula in Cincinnati, and the board priced that match about where their records said it should be. The gap is a parlay, and parlays look cheap because they multiply. The only price on this page worth arguing with was 37¢, and the argument against it was 233,614 contracts of offers and two September wins, while the argument for it was one June afternoon in Berlin and four break points that never landed. Sabalenka's 99 weeks at No. 1 were taken from her on Wednesday without her hitting a ball, and the list made it official on Monday. On Thursday the title could only be taken from her with a racket, and at 63¢ the market did not expect it. It was not taken on Thursday. It was taken on Saturday, by the name the gap had on it: Rybakina, 6-4, 5-7, 6-2, and the 36¢ title contract on Sabalenka settled at zero two days after the 63¢ match contract paid. The gap between a third and an eighth turned out to be exactly one match wide, and the market had named the match.
The Sabalenka-Pegula line is off the board now, but for the next match you price, the live odds screen is where to shop the moneyline across every major book against what Kalshi is showing. If pricing a single semifinal is not your game, OddsShopper's free expert picks cover the tournament the conventional way. For the wider board, the US Open odds comparison across Kalshi, Polymarket and the sportsbooks maps the whole field, and the daily Kalshi picks hub grades the panel's calls in public.
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Prices quoted are the September 9 snapshot named above and the settled Kalshi trade log re-pulled on September 16, 2026; the match and title markets are finalized and no longer trade.
More on this: Sabalenka Vs Rybakina Odds: 7-7 On Hard Courts. The Board Picked A Side · Pegula Vs Navarro Odds: The Crowd Kept Buying Navarro. The Price Held · Gauff vs Pegula Odds: Did Kalshi Price The Final Right?
