Defending champion Carlos Alcaraz and top-ranked Jannik Sinner are one match away from another high-stakes meeting in the Wimbledon semifinals.

Both men reached the quarterfinals on Sunday, with Alcaraz holding off an attempted comeback by Ugo Humbert to win 6-3, 6-4, 1-6, 7-5 on Centre Court. Sinner then beat Ben Shelton 6-2, 6-4, 7-6 (9) on No. 1 Court after saving four set points in the third set.

Alcaraz beat Sinner in five sets in the French Open semifinals in June en route to his first title at Roland Garros, and the two would meet again in the last four if they win their next matches. Alcaraz will play the winner between No. 12 Tommy Paul and Roberto Bautista Agut, while Sinner — this year’s Australian Open champion — faces No. 5 Daniil Medvedev or No. 10 Grigor Dimitrov.

Alcaraz and Sinner came up with some spectacular shots when it mattered on Sunday.

Alcaraz’s match against Humbert had seemed all but over when the Spaniard clinched the second set by chasing down several seemingly out-of-reach shots on set point, even falling over after hitting one forehand and quickly getting back up to get to the next ball.

Asked to describe his play on that point, Alcaraz just said: “Unbelievable, I guess.”

Humbert nearly staged a surprising comeback and threatened to take the match into a fifth set when he held three straight break points for a 5-3 lead in the fourth. But Alcaraz came back to win that game with the help of a couple of aces, then broke for a 6-5 lead by hitting a deep forehand winner.

He set up match point with one of his delicate forehand drop shots and converted it with a service winner.

“I felt great playing today, I think I played at a really high level,” Alcaraz said.

Sinner had to come from 4-1 down in the third set and held for 5-5 after wrapping his racket behind his back and hitting the ball between his legs to get it over the net, then followed it up with a forehand passing shot to clinch the game.

“That was just luck,” Sinner said about his shot.

Sinner then saved one set point at 6-5 and three more in the tiebreaker before converting his second match point when the hard-serving Shelton double-faulted.

Shelton was trying to reach his first Wimbledon quarterfinal but was coming off three straight five-set wins, including one over Denis Shapovalov that finished on Saturday.

Sinner is into the last eight for the third year in a row, having lost to Novak Djokovic in last year’s semifinals.

Earlier, French Open runner-up Jasmine Paolini reached her first Wimbledon quarterfinal when Madison Keys had to retire with a leg injury at 5-5 in the third set of their fourth-round match. Donna Vekic also advanced after beating Paula Badosa 6-2, 1-6, 6-4 in a stop-start match on No. 2 Court that was interrupted several times because of rain. Vekic will also be playing in her first Wimbledon quarterfinal, in her 10th appearance at the grass-court Grand Slam tournament.

Keys had served for the match at 5-2 in the last set but then started limping more and more and needed a medical timeout to get her left leg worked on after Paolini made it 5-4. She had her left thigh taped as she served for the match for a second time but was broken again — double-faulting on break point — and was in tears by the end of that game, with her movement clearly restricted.

Keys tried to play on, but the American finally went to the net to tell the chair umpire on No. 1 Court that she was retiring after Paolini hit an ace for 15-15 in the final game.

The Italian had won the first set 6-3, before Keys won the second 7-6 (6).

Keys had been two points from the win when the score was deuce at 5-2 in the third.

“I’m so sorry for her. To end the match like this, it’s bad,” Paolini said in her on-court interview. “What can I say? We played a really good match. It was really tough. A lot of ups and downs. I’m feeling a little bit happy, but also sad for her. It’s not easy to win like that.”

Paolini is the fifth Italian woman to reach the Wimbledon quarterfinals in the professional era, and will try to become the first to make the semifinals. She will face the winner between No. 2 Coco Gauff and 19th-seeded Emma Navarro, who played later on Centre Court.

Keys, the 2017 U.S. Open runner-up, was trying to reach the last eight for the second year in a row at the All England Club, and third time overall.