This turned out to be the breakthrough moment for Fritz in his 33rd Grand Slam participation.

He lost in the quarter-finals of the US Open to Novak Djokovic in 2023, lost twice in the last eight at Wimbledon in 2022 and in July this year, and suffered a quarter-final defeat at the Australian Open in January.

After sharing a close set twice, the decisive moment came deep into the third set when Zverev looked to have the momentum after regaining an early break.

He missed an easy backhand on break point at 4-4, allowing Fritz to hold the ball, but the fourth-seeded player then made three forehand errors to fall behind 0-40.

Zverev saved those three set points, but Fritz finally broke through on the fifth attempt.

Fritz, who also won from two sets down against Zverev at Wimbledon this year, was able to neutralize the German’s strong first serve and remained the strongest with the finish in sight, while also hitting powerful serves himself.

He took the initiative in the fourth-set tiebreak by taking the first point on Zverev’s serve and won a gruelling 24-point rally for the second break and a 5-2 lead.

Fritz hesitated for a moment and hit a nervous forehand wide, but Zverev made two more errors to decide the outcome.

Zverev said afterwards that he had not felt so angry and disappointed after a match in “a long time”.

“I played terribly,” said Zverev, who was uncharacteristically weak in the final set and complained about his racquet throughout as he chased his first Grand Slam title and a third US Open semifinal.

“I just don’t have any answers at the moment. He played a pretty good game. I didn’t do anything to deserve to win.”

On the prospect of an all-American semifinal against Tiafoe, Fritz said: “I know the crowd is eager to see me play against Frances so we can get an American in the final.

“That could get crazy, so I’ll see what happens. But either way, I’m ready.”

Britain’s Jack Draper is one of the remaining players in the top half of the draw and will play Alex de Minaur in the quarter-finals on Wednesday.