This was Fritz’s breakthrough in his 33rd Grand Slam appearance.

He lost to Novak Djokovic in the quarterfinals of the US Open in 2023, lost twice in the last eight at Wimbledon in 2022 and in July this year, and suffered a quarterfinal loss at the Australian Open in January.

After two close sets were shared, the decisive moment came deep in the third set when Zverev seemed to gain the upper hand after an early break.

At 4:4, he missed a simple backhand on the break point, allowing Fritz to hold on to his serve. The fourth-seeded player then made three forehand errors and fell behind 0:40.

Zverev fended off these three set points, but Fritz finally made the breakthrough on the fifth attempt.

Zverev will feel he had his moments, but Fritz won because he was able to neutralise Zverev’s booming first serve and remained the more solid player with the finish line in sight.

He took the initiative in the fourth set tiebreak, taking the first point on Zverev’s serve and then completing a grueling 24-point rally to earn the second break and a 5-2 lead.

Fritz stumbled briefly and missed a nervous forehand, but Zverev made two more errors and secured the result.

Zverev, who is hoping for his third US Open semifinal and his first Grand Slam title, put in an unusually weak performance in the final set, complaining about his racket throughout.

Briton Jack Draper is one of the remaining players in the top half of the field and will play Alex de Minaur in the quarter-finals on Wednesday.