World No. 1 Jannik Sinner withdrew from the 2026 US Open on Friday, August 21, with a right knee injury, and Polymarket's "2026 Men's US Open Winner" market repriced within hours. As of 2026-08-30 12:06 UTC, with the main draw starting today: Carlos Alcaraz is the field's favorite at 25c bid / 26c ask, Alexander Zverev trades 23.0c/23.1c, Novak Djokovic 9.1c/9.7c, and Sinner's own contract - frozen since the withdrawal - sits at essentially 0, with no bid and a 0.1c ask. Numbers below are from Gamma and the CLOB, fetched at that time.
01The withdrawalA 44-3 season, then a knee that wouldn't clear
Sinner hadn't played a match since winning Wimbledon in July. He withdrew from the Montreal and Cincinnati warm-up events first, then made it official for the US Open on August 21: "I still need more time to recover from my right knee issue," he wrote, adding that "New York has a special place in my heart." It is the first Grand Slam he has missed since his major debut at the 2019 US Open - a run that included a 2026 season record of 44-3 with six titles, among them the first five ATP Masters 1000 events of the year (Indian Wells, Miami, Monte-Carlo, Madrid, Rome). The 2026 US Open's main singles draw begins today, August 30, without its top seed.
02The chartDoubt priced in for days, certainty priced in in hours
Sinner's contract had already been drifting for days before the official call - from 50.5c on August 17 down to a 32-35.5c band by August 20-21, as his Montreal and Cincinnati withdrawals raised doubt about his fitness without confirming anything. Then, between 12:00 and 18:00 UTC on August 21, it fell from 35.5c to 0.15c - the market converting days of doubt into near-certainty within a single six-hour window once the withdrawal was official, and settling at a final 0.05c print. Alcaraz absorbed the biggest single jump: 25.5c to 33c in the same window, +7.5 points. He has since eased back to 25.5c as the rest of the seven-and-a-half-point draw - not just one player - settled into the gap Sinner left.
03The field nowAlcaraz and Zverev, 2.45c apart
2026 US OPEN WINNER (M) PRICE 24H
Carlos Alcaraz 25.5c -2.0c
Alexander Zverev 23.05c --
Novak Djokovic 9.4c -0.4c
Taylor Fritz 8.15c +0.9c
Ben Shelton 6.3c +0.85c
Felix Auger-Aliassime 3.6c +0.5c
Jakub Mensik 2.8c +0.2c
Daniil Medvedev 2.75c +0.6c
Jannik Sinner 0.05c -35.45c
Zverev, at 21.25c the morning of the withdrawal, very nearly doubled - 11.25c to 21.65c the same six hours - and has kept climbing since, to 23.05c, closing to within 2.45c of Alcaraz. That is a tighter title race than the ladder looked a week and a half ago, when Sinner alone traded above 30c and everyone else split the rest of the field. Djokovic's 9.4c is essentially unchanged by the news - the market isn't pricing the 40-year-old as a fresh beneficiary of a thinner draw, just a steady outsider chance that was already there.
04Reading the bookA thin dime on Zverev, real size behind Alcaraz
TOP OF BOOK, 2026-08-30 12:06 UTC
Alcaraz bid 0.25 x 9,159 ask 0.26 x 35,942
Zverev bid 0.23 x 6,403 ask 0.231 x 23,391
Zverev's book is the tighter of the two - a single tenth of a cent between bid and ask, with resting size on both sides in the 6,000-23,000 share range. That is a price the market has converged on with little disagreement left to resolve. Alcaraz's spread is ten times wider at a full cent, and the ask alone carries nearly 36,000 shares - a lot of size willing to sell Alcaraz-Yes at 26c without anyone having to chase the price higher to get filled. Read together, the book says the field agrees Zverev is worth almost exactly 23c, and is still working out whether Alcaraz belongs closer to 25c or 26c.
05How a contract dies before a point is playedSinner's market closed; the other 21 are still open
The Gamma API flags Sinner's contract closed: true, while
every other player in the same event - Alcaraz, Zverev, Djokovic, all the
way down the ladder - still shows closed: false and is still
trading. A "tournament winner" event on Polymarket isn't one market; it's a
separate Yes/No contract per contender, and each one resolves independently
the moment its own outcome is settled. Sinner's couldn't wait for a champion
to be crowned in two weeks, because withdrawing made his "Yes" impossible
the moment it became official - so his contract closed on August 21, more
than a week before the tournament's first ball was struck, while the
remaining contenders keep trading against each other until someone actually
lifts the trophy.
Twenty-two contenders, one screen
In polymarket-tui, the event's outcome table lists every contender in the ladder together - price and 24-hour change side by side - so a move like Sinner's shows up next to Alcaraz's and Zverev's instead of requiring a lookup per player.
$ uv tool install polymarket-tui
$ polymarket-tui
No account is needed to browse markets, books, and charts. The install page has Homebrew and one-liner options.