Aryna Sabalenka has won 18 straight matches at the US Open, 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 publishes Monday closes Sabalenka's run at 99 weeks. What happens next is 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, Kalshi's match market has Sabalenka at 63¢ bid, 64¢ ask, and Pegula at 36¢ bid, 37¢ ask. Read as a probability, the two-time defending champion is a 63 to 64 percent favorite. On the same exchange's tournament board, Sabalenka is 36¢ to 37¢ to win the whole thing and Pegula is 12¢ to 13¢.
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 is that it is not, because the gap is 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 is a 6-0 third set that Pegula won. The order book is where the argument ends, and it ends with 233,614 contracts of Pegula sitting for sale at the current price and just above it. I will get to who is 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 as I write, 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. The winner plays Rybakina. Sabalenka and Pegula play each other, in the night session, which opens at 7 p.m. ET.
Three US Opens, 13 Matches, One 6-0 Set
Sabalenka and Pegula have met 13 times on tour and Sabalenka leads 9-4, including both previous US Open meetings. 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 is 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 is the market's estimate of whether the third one goes the same way, and the freshest evidence says the pattern can 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 have not played since.
That is the case a 36-cent buyer is 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 has 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 matter 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 has been. 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. Since then the price has 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 has printed 37¢ in every hour since 10 a.m., with a handful of fills at 36¢ after 2 p.m. and a 36¢ bid under it that is 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 tape 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.
| Market (Kalshi Event) | Contract | Bid | Ask | Contracts traded | Open interest |
|---|---|---|---|---|---|
| Sabalenka Vs Pegula, Semifinal (Thu. Night) | Aryna Sabalenka wins | 63¢ | 64¢ | 32,716 | 30,319 |
| Sabalenka Vs Pegula, Semifinal (Thu. Night) | Jessica Pegula wins | 36¢ | 37¢ | 7,196 | 6,644 |
| US Open Women's Champion (KXWTA-26USO) | Aryna Sabalenka | 36¢ | 37¢ | 552,514 | 335,665 |
| US Open Women's Champion (KXWTA-26USO) | Elena Rybakina | 25¢ | 27¢ | 477,891 | 296,278 |
| US Open Women's Champion (KXWTA-26USO) | Jessica Pegula | 12¢ | 13¢ | 399,203 | 302,623 |
| US Open Women's Champion (KXWTA-26USO) | Mirra Andreeva | 12¢ | 13¢ | 316,495 | 290,239 |
| US Open Women's Champion (KXWTA-26USO) | Coco Gauff | 11¢ | 14¢ | 800,810 | 537,044 |
Bid and ask are the live quotes on each yes contract as of September 9, 2026, at 3:08 p.m. ET; contracts traded and open interest are lifetime for each contract, all from one pull of Kalshi's public market data. Gauff and Andreeva were mid-match at pull time, which is why Gauff's quote is three cents wide. The five title midpoints sum to 100.
More live boards from the same panel: US Open men's title board (Alexander Zverev 43¢ bid, Ben Shelton 37¢) · US Open women's title board (Rybakina 25¢ bid, 27¢ ask)
The row to sit with is Pegula's title line, because it has 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 has since won the quarterfinal, and she is 12¢ bid, 13¢ ask. The tape in between is 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 is a price that says the two matches she has left are 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 is saying that if Pegula beats Sabalenka on Thursday, she is roughly a one-in-three shot on Saturday, and that if Sabalenka wins, she is better than even money.
Whether 34 percent is stingy depends entirely on who is on the other side of the net on Saturday, and the other half of the draw has already told us. The three names left there add up to a 51-cent midpoint on the title board, and Rybakina, the newly minted No. 1, holds 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 comes through instead, she is the woman who beat Pegula 6-2, 6-4 in the Cincinnati final three weeks ago. And if it is Andreeva, the player the in-play market liked at pull time, Pegula has never played her, so a quarter of the bottom half is 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 has not been beaten by lately is the one she has never met. It is the head-to-head against the other side of the draw, and Pegula does not own that one.
So the gap has a name, and the name is mostly Rybakina. That leaves the semifinal price itself, which is where the argument actually lives. 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. Re-run that arithmetic at whatever price is on the screen when you read this; the numbers will have moved, and this page will not.
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 has traded in its life. Getting her price to 40¢ means buying every one of them. The bid side under her is real too, 20,846 contracts at 35¢ and 33,437 at 34¢, so a seller cannot 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 starts at 65¢, where 33,821 sit, and 66¢, where 90,074 do.
That is what a settled price looks 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 says that whoever is quoting has no interest in letting a few thousand contracts of enthusiasm move her. The crowd that bought 32,000 contracts of Sabalenka since Tuesday night has not tried. If there is an edge on Pegula at 37, taking it means buying into that wall, and the wall has shown its size.
The Case For Pegula At 37, Argued Honestly
The 37 cents may well be right. What follows is what it would need to be wrong about, because the underdog case here is 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 say she is comfortable in the third hour, and Thursday's match, if the first two here are a guide, will have one.
The counter is everything Sabalenka has 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 has 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 is the first break point Pegula earns, because last September's four went begging and a year of three-set wins says she has been finishing them since. The market's 37¢ already assumes she plays well and loses a close one, the way she has twice. It is not priced for the first one to land.
More on this: Pegula Vs Navarro Odds: The Crowd Kept Buying Navarro. The Price Held · Gauff vs Pegula Odds: Did Kalshi Price The Final Right? · Barcelona Vs Feyenoord Odds: Does The Favorite Survive The Fee? · The Longest Shot On This Board Might Be The Best-Kept Secret · MAC Championship Odds: Ohio Never Has To Play The Favorite
Where The Real Question Sits
So the thesis holds. The distance between a third of the semifinal and an eighth of the title is a second match against Rybakina, or against the woman who beat Pegula in Cincinnati, and the board prices that match about where their records say it should be. The gap is a parlay, and parlays look cheap because they multiply. The only price on this page worth arguing with is 37¢, and the argument against it is 233,614 contracts of offers and two September wins, while the argument for it is 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 makes it official Monday. On Thursday the title can only be taken from her with a racket, and at 63¢ the market does not expect it.
As the books post and move their Sabalenka-Pegula lines, 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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These are market prices and my own reading of them, not model estimates, not predictions of fact and not financial advice. Kalshi is a CFTC-regulated event-contract exchange (18+; availability varies by state). Prices quoted are the snapshot named above and will have moved by the time you read this.
