Sinner Withdraws From US Open, Win Probability Falls to 33%

Jannik Sinner's implied win probability in the US Open Men's Singles Winner market fell 16 percentage points to 33% after the world No. 1 withdrew from the 2026 US Open on August 21 due to a persistent right knee injury. The same injury sidelined him from the Masters 1000 events in Montreal and Cincinnati earlier this month, and his team confirmed he needs more recovery time before returning to competition.

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Why Jannik Sinner's US Open Chances Dropped to 33%

The withdrawal is the clear catalyst behind the 16-percentage-point drop in Sinner's implied win probability on prediction markets. Three days ago, both Kalshi and Polymarket priced the Italian at 49%, making him the consensus favorite. As of today, both platforms show him at 33%.

Prediction-market view

Resolved Sep 13, 2026

Final prices, venue by venue

This market settled on September 13, 2026, so nothing below is tradeable. These are the last prices each venue published before settlement, not live quotes.

That 33% figure deserves scrutiny. Sinner is out of the tournament. A withdrawn player holding a 33% implied probability is unusual, and it likely reflects residual positioning, slow-moving limit orders, or traders speculating on a late reversal of the withdrawal. The probability briefly touched 28% before recovering five points, suggesting some buyers stepped in at what they perceived as an overcorrection. But unless Sinner reverses course and enters the draw before the August 25 deadline, this contract resolves to zero.

Before the knee flared up, Sinner was having a historically dominant season: titles at Indian Wells, Miami, Monte Carlo, Madrid, Rome, and a second consecutive Wimbledon crown, where he defeated Alexander Zverev in the final on July 12. That resume explains why the market was reluctant to fully price out his chances even after the withdrawal announcement.

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Who Gained Ground After Sinner's Withdrawal?

The 16 points Sinner shed did not flow to a single rival. According to FanDuel's updated odds, Carlos Alcaraz is now the clear sportsbook favorite at +170, followed by Alexander Zverev at +350. Ben Shelton and Novak Djokovic sit further back at +850 each, with Taylor Fritz at +1400 and Arthur Fils at +2200.

The distribution tells you the market sees this as Alcaraz's tournament to lose, but not overwhelmingly so. An implied probability near 37% for Alcaraz (derived from the +170 line) means bettors still assign a roughly two-in-three chance that someone else lifts the trophy. That is a wide-open field by Grand Slam standards, where a single dominant favorite often commands 40% or more.

Zverev's position at +350 is notable given that Sinner beat him in the Wimbledon final just six weeks ago. The German has the game to thrive on hardcourt, but his Grand Slam conversion rate remains a concern. Shelton, the home favorite, and Djokovic, chasing history at 39, round out the realistic contender tier.

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Charting Sinner's Drop: From 49% to 33% in Three Days

The three-day chart reveals a near-vertical drop from 49% coinciding with the August 21 withdrawal announcement, followed by a brief dip to the period low of 28%, and then a partial recovery to the current 33%. The inflection point is unmistakable: this was not gradual sentiment drift. It was a single news event repricing the entire market in a matter of hours.

The bounce from 28% to 33% is the more interesting data point. It suggests a cohort of traders either betting on a late entry reversal or simply providing liquidity at levels they consider cheap for a withdrawn player. If Sinner formally confirms he will not enter, expect that 33% to compress toward zero as resolution approaches on September 13.

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The Case Against Sinner at 33%

The strongest bear case is simple: Sinner is not playing. A contract on a withdrawn player should, in theory, trade near zero. The fact that it holds at 33% points to market inefficiency rather than genuine belief.

Steelmanning the remaining bullish position requires acknowledging two narrow scenarios. First, Sinner has not yet passed the hard entry deadline. Grand Slam withdrawals have, in rare cases, been reversed when players recover faster than expected. Second, if the contract's resolution criteria define "winner" in a way that includes a late wild-card entry or similar mechanism, there could be a technical path.

Neither scenario is likely. Sinner stated publicly that he requires more time to recover, and the injury already cost him two Masters 1000 events. His team has given no indication of a return timeline. The knee issue, described as persistent, is the kind of injury that worsens with rushed comebacks on hardcourt surfaces.

For traders, the 33% price looks like dead money unless a reversal materializes that no credible source has reported. The more actionable question is whether Alcaraz at an implied 37% is too low given the weakened field, or whether the depth of the draw (Zverev, Shelton, Djokovic) makes this a genuine multi-contender race. For live prices across all contenders, see the US Open Men's Singles Winner odds hub.