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    2026 US Open Gets Underway: Alcaraz at 31 Cents, Sabalenka Leads Women's Board on Kalshi

    The 2026 US Open is underway at Flushing Meadows. Kalshi has Alcaraz at 31 cents to win men's singles, Sabalenka at 23 cents on the women's side.

    By PredictionMarkets.usTuesday, August 25, 20268 min read
    2026 US Open Gets Underway: Alcaraz at 31 Cents, Sabalenka Leads Women's Board on Kalshi

    The 2026 U.S. Open is now underway at the USTA Billie Jean King National Tennis Center in Flushing Meadows, and prediction market traders are watching two boards that look nothing like they did a month ago. On the men's side, Carlos Alcaraz carries the probability as the field's highest-ranked entrant after world No. 1 Jannik Sinner withdrew with a knee injury. On the women's side, two-time defending champion Aryna Sabalenka heads a market that is meaningfully more open than the men's draw.

    Kalshi — the CFTC-designated contract market that has become the primary regulated exchange for US Open tournament winner contracts — has logged over $7 million in trading activity on the men's singles board heading into tournament play, according to reporting by The Express. That depth of liquidity makes the Kalshi board one of the most efficient real-time probability gauges available for the final Grand Slam of 2026.

    Here is what the markets say as the balls start flying at Arthur Ashe Stadium.

    Men's Board: Alcaraz at 31 Cents, Zverev Pressing

    Carlos Alcaraz opens as the clear favorite on Kalshi's men's singles winner market, currently priced at 31 cents. That figure represents the market's real-time implied probability of Alcaraz winning the title — a contract that pays $1.00 if he does.

    That 31-cent price is actually a slight retreat from the 34 cents Alcaraz commanded when Sinner's withdrawal was first confirmed last week. The drift is informative. Alcaraz has not played a competitive singles match since April, when he sustained a right wrist injury after winning his opening match at the Barcelona Open. He missed both the French Open and Wimbledon due to the injury, according to The Associated Press. The market priced him as the clear favorite the moment Sinner stepped aside, then spent the week quietly absorbing the reality that the defending champion arrives in New York without any warm-up competitive data since the spring.

    Alexander Zverev sits at 20 cents, firmly in second. The gap between Alcaraz at 31 cents and Zverev at 20 cents is relatively narrow for a pre-tournament favorite at a Grand Slam — it reflects the genuine uncertainty around Alcaraz's match sharpness after an extended absence. Zverev enters the tournament off one of his strongest North American hardcourt stretches, having reached back-to-back Masters finals even before Sinner's absence changed the probability landscape.

    Novak Djokovic trades at 10 cents. The three-time US Open champion remains a non-trivial tail risk for any path to the title. In conditions — heat, humidity, best-of-five — where younger opponents can falter against a player who has navigated Flushing Meadows' specific demands better than almost anyone in the Open Era, the market's 10-cent pricing reflects that specific scenario.

    Ben Shelton sits at 8 cents and Arthur Fils at 7 cents. Both represent the "American underdog" tier: big serving, flat-swinging hardcourt games that are genuinely dangerous at Arthur Ashe Stadium, where the fast surface amplifies first-strike tennis. Shelton in particular has become the most actively traded long-shot position on the board, with traders attracted to a game style that can produce sudden upsets in best-of-five format.

    Kalshi's men's board carries 34 individual player contracts — one for each prominent entry — and has traded over 6.6 million contracts across those markets heading into tournament play, according to reporting by The Express. That scale of engagement makes the US Open one of the highest-volume single-event boards on the exchange.

    The Alcaraz Fitness Question

    Before the first-round singles results even start filtering in, traders had an unusual data point to observe: Alcaraz is competing in US Open mixed doubles alongside Serena Williams. Kalshi lists no mixed doubles winner market — the exchange's tennis coverage runs to singles winner boards only — but that does not make the doubles action irrelevant to the 31-cent singles contract.

    Mixed doubles first-round play began earlier in the tournament schedule, giving traders their first live footage of Alcaraz moving on a hard court in four months. Every service game, every cross-court forehand, every split-step reveals information the market could not previously price. A player who moves cleanly through a doubles match without compensation patterns in his footwork or reduced swing speed represents meaningful positive evidence about the wrist. The singles board will absorb that signal.

    That is precisely the dynamic that keeps Alcaraz at 31 cents rather than 36 or 37. The market is not pricing just his talent — it is pricing a fitness question that has been open since April. Tournament play is when that question starts to close.

    Women's Board: Sabalenka Favored, but the Field Is Genuinely Open

    The women's prediction market tells a different story: it is substantially more dispersed than the men's, and the recent history of women's Grand Slam tennis is the reason.

    Aryna Sabalenka leads the women's singles board at 23 cents on Kalshi, according to data reported by Yahoo Sports. The Belarusian is the two-time defending US Open champion and enters New York having won 82% of her hard-court matches in 2026. But 23 cents implies a competitive landscape where no single player commands dominant probability — the market is pricing a legitimate, multi-player race.

    Iga Swiatek follows at 17 cents. That price reflects a persistent underpricing pattern that traders have noted throughout the summer hardcourt swing: Swiatek's reputation as a clay-court specialist causes markets to discount her on hard surfaces, even though she captured the US Open title in 2022 and carries a career record of 24-6 at Flushing Meadows, per Kalshi's official market coverage. Her hardcourt win rate in 2026 has been strong, and she won the National Bank Open in Montreal last month. The 17-cent market implies a roughly 17% chance — a number that many traders consider undervalued relative to her hardcourt results.

    Coco Gauff trades at 11 cents, carrying the weight of home-crowd advantage at a tournament where the Arthur Ashe Stadium atmosphere is uniquely loud and favorable for American players. Naomi Osaka sits at 8 cents, a remarkable position that reflects her strong run of form since returning to competitive tennis — she reached the Wimbledon quarterfinals and a grasscourt final in Bad Homburg over the summer. Mirra Andreeva, the youngest player in the world top 10, is priced at 7 cents.

    The dispersal of this market — six players trading between 7 and 23 cents — is consistent with women's Grand Slam tennis in recent years, which has produced varied champions across different conditions and surfaces. The women's draw is not a two-horse race.

    Platform-by-Platform: Where to Track US Open Odds

    Kalshi is the primary CFTC-designated contract market for US Open singles winner contracts. The men's board carries 34 player markets; the women's board is structured similarly. Contracts are priced between $0.01 and $0.99, representing real-time implied probability. A winning contract pays $1.00 per share.

    Robinhood, which distributes markets through Kalshi's regulated infrastructure, also carries individual match contracts for US Open singles play — allowing traders to take positions on specific first-round matchups rather than the full tournament winner. These match-level contracts update live as sets are completed and are how tournament-level winner prices receive their real-time information input. When Alcaraz wins his first-round match convincingly and moves freely, the 31-cent tournament winner contract is the first place that information will appear.

    Polymarket (operating through QCX LLC, its CFTC-regulated US entity) offers sports prediction markets including US Open winner contracts. The women's market on Polymarket shows Sabalenka as the leader with consistent pricing relative to the Kalshi board, reflecting efficient arbitrage between regulated platforms on high-liquidity events.

    Watching the First Round

    First-round singles play began at the USTA Billie Jean King National Tennis Center this week, with Kalshi and Robinhood running match-level event contracts for individual matchups across Arthur Ashe Stadium, Louis Armstrong Stadium, and the field courts.

    For the tournament winner markets, the most significant first-round events are the ones involving the top of the board. Any Alcaraz match result — win, loss, or withdrawal — moves the 31-cent contract immediately and substantially. A Zverev loss to an unseeded opponent would similarly compress the field. These are the moments where prediction markets earn their reputation for faster price discovery than traditional odds-setting.

    Traders following the tournament will want to watch how the Alcaraz price responds to his first match: if he wins cleanly in straight sets, expect a move toward the mid-30s as the fitness uncertainty partially resolves. If he shows any sign of protecting the wrist or goes to a tight third set, the 31-cent contract is likely to soften toward the low 20s and Zverev becomes the live co-favorite.

    FAQ

    How do Kalshi's US Open odds work? Kalshi lists binary event contracts for each player in the tournament. A contract priced at 31 cents means the market assigns that player approximately a 31% chance of winning the title. You buy the contract, and it pays $1.00 if the player wins; it expires at $0 if they lose. Contracts can be sold before resolution if a player you hold is knocked out or your view changes.

    Why is Alcaraz's price lower than expected for a defending champion? Alcaraz sustained a right wrist injury in April and has not played competitive singles tennis since then. He missed the French Open and Wimbledon. The market is pricing both his talent — which is the clear favorite in the field — and the uncertainty about his match fitness after a four-month competitive absence. As he plays matches and traders observe his movement and stroke production, that uncertainty premium will compress.

    Is the women's market less certain than the men's? Yes, by a meaningful margin. The top women's contract (Sabalenka, 23 cents) is lower than the top men's contract (Alcaraz, 31 cents), meaning the market distributes probability across a wider set of plausible outcomes in the women's draw. No single player commands the kind of probability concentration that Alcaraz holds on the men's side.

    Can I trade individual US Open match outcomes? Yes. Both Kalshi and Robinhood carry first-round match contracts, which settle when the match completes. These are separate from the tournament winner contracts. Match contracts are how the prediction market ecosystem generates the most rapid real-time price discovery during tournament play.

    What is Polymarket's US Open coverage? Polymarket operates US-accessible sports prediction markets through QCX LLC, its CFTC-regulated entity. It carries US Open tournament winner contracts. US users on Polymarket should note that political and other non-sports markets are handled separately through the global platform, which is not accessible to US users.

    Conclusion

    The 2026 US Open is the final Grand Slam of the tennis calendar, and the prediction market at Flushing Meadows is running at its most liquid point of the year. Carlos Alcaraz at 31 cents is the men's favorite by a clear margin — but 20-cent Zverev, 10-cent Djokovic, and a competitive cluster of Americans behind them reflect how much information the market still needs to price correctly over the next two weeks.

    On the women's side, a 23-cent Sabalenka leads a market spread across multiple serious contenders, none of whom commands dominant probability in a draw where the recent track record of women's Grand Slams has consistently resisted easy prediction.

    PredictionMarkets.US tracks live tournament winner odds and match-level contracts for both Kalshi and Polymarket throughout the US Open. Prices update in real time as rounds are completed.

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