LONDON — 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 Sunday.

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.

“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 was trying to reach the last eight for the second year in a row at the All England Club and third time overall.