2026 Tennis Grand Slam Tracker — US Open

The US Open main draw begins August 24. Kalshi's men's book runs $53,722 a day, the women's $13,923, and the prices are exactly what a seeding sheet would predict: Sinner 49.5%, Alcaraz 14.5%, Zverev 11.5%, Djokovic 6.5%. Sabalenka 26.5%, Swiatek 15%, Rybakina 11.5%, Gauff 8.5%.

The flow is not what a seeding sheet would predict.

Ben Shelton at 5.5% is the deepest leg in the men's draw, taking $12,049—more than Alcaraz at 14.5% ($9,157) and more than Sinner at 49.5% ($8,661). The market's largest position is on a player it gives a one-in-eighteen chance.

Rafael Jodar at 4.5% holds 236,275 contracts of open interest, the most of any man in the field—above Alcaraz's 215,600 and half again Sinner's 162,841. On the women's side, Alexandra Eala at 3.5% holds 109,022 contracts, more than five times Sabalenka's 19,235 and more than Swiatek, Gauff and Osaka combined.

Two different books, same structure: the favorites carry the price and the young outsiders carry the position.

A new venue is arriving. Gemini's Titan DCM certified US Open men's singles binary contracts with the CFTC this week. Kalshi has had this market to itself; it is about to have company, and the cross-venue spread on a two-week tournament will be the first real test of whether a second listing venue tightens tennis pricing or fragments it.

Kalshi's Categorical against Manifold's grand-slam finalists book. Kalshi carries essentially all of the flow—Manifold's men's US Open market has traded $14 in 24 hours—so read Manifold as an independent price mark rather than a spread.

Sinner at 49.5% is the tightest favorite pricing of any major this year: the book gives one man an even-money shot and splits the remaining half across a field of a hundred and twenty-seven.

Sabalenka 26.5%, Swiatek 15%, Rybakina 11.5%, Gauff 8.5%, Osaka 8.5%, Andreeva 7.5%, Pegula 5.5%. Where the men's book has a single dominant name, the women's has seven players inside twenty points—the flattest major draw on the board.

Manifold's women's book ($903) is the only genuine cross-exchange mirror in this workspace, and it agrees closely: Gauff 8.5% on both, Andreeva 6.2% against Kalshi's 7.5%.

The 2026 WTA grand slam book alongside prices the season rather than the fortnight, and it is the reconciliation check: Sabalenka is 28% to win any slam this year against 26.5% to win this one, with the Australian and French already gone. That is close to a statement that the US Open is her last realistic chance.

The full-year ATP book at $3,375 a day. Sinner 50%, Shelton 7.0%, Djokovic 5.0%, Fritz 4.0%, Medvedev 1.5%.

Shelton appears here at 7.0% with 10,003 contracts of open interest, and at 5.5% in the US Open book with $12,049 of today's flow. Across both horizons he is the name the market keeps buying and declining to reprice.

Djokovic is the other tell: 6.5% for this tournament against 5.0% for the whole season, which is internally inconsistent unless the market believes New York is his only remaining shot—the same read the Sabalenka numbers give on the women's side.

Whether the draw ceremony reprices Shelton and Jodar. Both carry position out of proportion to price. A friendly quarter for either one is the most likely single event to move this book before a ball is struck.

Alcaraz at 14.5%. He is the second favorite and Kalshi lists a separate contract on whether he plays at all. Fourteen and a half percent for a two-time champion is a price with a participation discount already in it—read the two markets together, not separately.

Eala's 109,022 contracts. The largest open-interest position in the women's draw sits on a 3.5% name. If that is informed rather than sentimental, it shows up in the first week.

The Gemini Titan listing. First US Open with a second CFTC-regulated venue quoting the men's singles. Watch whether Kalshi's spreads tighten when the draw is released, and whether volume splits or grows.

The season books collapsing into this one. Sinner 50% for the year and 49.5% for the fortnight; Sabalenka 28% and 26.5%. Both season markets have stopped pricing anything except New York, and after September 13 they resolve.

The two favorites, side by side. Sinner's 49.5% is doing something unusual against the season book: he is 50% to win any 2026 ATP slam and 49.5% to win this one—the year-long market and the two-week market are the same number, which means the season book has effectively already resolved to the US Open.

Sabalenka's 26.5% against 28% for the season shows the same collapse, one tier less extreme.