Ben Shelton US Open at 36% After Alcaraz Upset | Polymarket

Ben Shelton's U.S. Open championship chances have exploded after the biggest victory of his career.

Shelton eliminated defending champion Carlos Alcaraz in a five-set quarterfinal thriller Tuesday night, sending the top-ranked American into the semifinals and completely reshaping the men's title market.

Polymarket now gives Shelton approximately a 36% chance to win the 2026 U.S. Open.

Alexander Zverev leads the current board near 44%, while Shelton has moved into a clear second position. Frances Tiafoe, who will face Shelton in Friday's semifinal, is around 10%.

More than $23 million has already been traded across the men's championship market.

Ben Shelton U.S. Open Chances Jump to 36%

The move is enormous compared with where Shelton stood earlier in the tournament.

Before the quarterfinal, Shelton was still trading in the single digits on several championship boards.

That changed when he defeated Alcaraz 6-7, 6-1, 6-3, 1-6, 7-6 inside Arthur Ashe Stadium.

The match lasted four hours and 28 minutes.

Shelton finally closed it with a 146 mph ace at 3:33 a.m., producing the latest finish in U.S. Open history.

It was also Shelton's first career victory over a Top 3 opponent.

The result immediately removed the defending champion and former market favorite from the championship equation.

That probability had to go somewhere.

A large portion moved toward Shelton.

Shelton Ends Alcaraz's Title Defense

Alcaraz entered the quarterfinal as the player to beat.

Winners & Whiners covered his championship probability at 56% on Kalshi before the Shelton matchup.

Alcaraz entered the quarterfinal as the clear U.S. Open favorite.

Shelton changed that in one night.

His serve proved particularly important late in the match, allowing him to shorten points and repeatedly escape pressure.

Alcaraz fought back after falling behind two sets to one and dominated the fourth set.

The fifth was far tighter.

Neither player could create enough separation, sending the deciding set into a 10-point tiebreak.

Shelton eventually finished the match with his biggest weapon.

The win snapped Alcaraz's 18-match Grand Slam winning streak.

Shelton vs Tiafoe Semifinal Is Already Set

Shelton's reward is an all-American semifinal against Frances Tiafoe.

Tiafoe reached the final four by surviving his own five-set quarterfinal against Alex Michelsen.

That guarantees an American man will play in Sunday's championship match.

It also gives Shelton a very different challenge from the one he faced against Alcaraz.

The market currently views Shelton as the stronger championship candidate.

Polymarket has Shelton near 36%, while Tiafoe is around 10%.

That does not mean Shelton has a 36% chance of beating Tiafoe specifically.

The outright market also accounts for the possible final and the players remaining on the opposite side of the draw.

Still, the gap shows how dramatically traders have upgraded Shelton after Tuesday night's upset.

Zverev Remains Ahead of Shelton

Alexander Zverev currently sits above Shelton at approximately 44%.

There is an important difference between their positions.

Shelton already owns a semifinal spot.

Zverev still has to win Wednesday night's quarterfinal against Botic van de Zandschulp.

If Zverev advances as expected, he will remain one of the clearest championship threats in the draw.

If he loses, Shelton's probability could rise considerably again.

That makes Wednesday another important day for the men's outright market even though Shelton will not play.

Can Shelton Win His First Grand Slam?

Shelton has been here before.

He reached the U.S. Open semifinals in 2023 before losing to Novak Djokovic.

This run feels different.

Shelton now has more experience, a stronger résumé and a victory over the defending champion behind him.

He also defended his Montreal title earlier this summer, confirming that his power game can hold up against elite competition on North American hard courts.

Winning the U.S. Open would still require two more matches.

But the path no longer looks theoretical.

Shelton is already in the semifinals.

One more victory would put him in his first Grand Slam final.

How the Ben Shelton Polymarket Contract Works

The Shelton contract is part of Polymarket's 2026 men's U.S. Open winner market.

A Yes position near 36 cents corresponds with an implied probability close to 36%.

If Shelton wins the men's singles championship, winning Yes contracts settle at $1.

If Shelton is eliminated, those contracts resolve at $0.

The price can continue changing before resolution.

Friday's semifinal, Zverev's quarterfinal and developments elsewhere in the draw can all affect the market.

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Eligible new users can currently use Polymarket promo code WINNERS when registering where available.

The current Winners & Whiners offer provides a $20 trading bonus after an eligible $10 deposit and qualifying trade.

Eligibility, geographic restrictions and promotional terms apply.

Prediction-market positions involve financial risk and can lose their full purchase value.

Ben Shelton Is Suddenly a Major U.S. Open Title Threat

Shelton entered Tuesday night as an underdog trying to stop the defending champion.

He left Arthur Ashe Stadium as one of the two strongest remaining championship candidates.

Polymarket now puts Shelton's U.S. Open chances around 36%.

The next challenge is Tiafoe.

For the first time in Shelton's career, however, the market is treating him less like a dangerous outsider and more like a player who could actually leave New York with the trophy.