LONDON — Jannik Sinner advanced to the Wimbledon quarterfinals despite hurting his right elbow in a fall and dropping the first two sets Monday night, because his opponent, Grigor Dimitrov, had to quit with an injured pectoral muscle.

The No. 1-seeded Sinner hadn’t dropped a set in the tournament until falling behind No. 19 Dimitrov 6-3, 7-5. But at 2-all in the third set, Dimitrov stopped playing.

It’s the fifth consecutive Grand Slam tournament where the 34-year-old Dimitrov failed to complete a match. He also did it at the Australian Open in January and the French Open in May, plus last year’s Wimbledon and U.S. Open.

“He’s been so unlucky in the past couple of years. An incredible player. A good friend of mine, also. We understand each other very well, off the court, too,” Sinner said. “I hope he has a speedy recovery.”

On the last point against Sinner, Dimitrov served and immediately clutched his chest with his left hand. He took a few steps and crouched, before sitting on the grass. Sinner walked over to that side of the court to check on him.

“My pec,” Dimitrov told Sinner.

Dimitrov — a three-time major semifinalist, including at Wimbledon in 2014 — then went to the sideline, sat in his chair and was checked by a trainer and doctor. As Dimitrov talked with them, Sinner knelt nearby. After a delay of a few minutes, Dimitrov walked toward the locker room with the medical personnel.

Soon, he reemerged and said he couldn’t continue.

“I don’t take this as a win, at all,” Sinner said. “This is just a very unfortunate moment to witness for all of us.”

Two hours earlier, it was Sinner down on the ground and seemingly in trouble. He was hurt in the opening game, when his foot gave out from under him and he slipped and fell behind a baseline, bracing his fall with his right hand while still holding his racket.

During a medical timeout while trailing 3-2 in the second set, Sinner winced as a trainer massaged the elbow. Sinner’s coaches, Darren Cahill and Simone Vagnozzi, looked on from their box with concern.

Sinner was given a pill to take and play resumed. He frequently shook his right arm or rubbed his elbow between points.

The 23-year-old Italian is a three-time Grand Slam champion who will play No. 10 Ben Shelton of the United States for a berth in the semifinals. Sinner leads the head-to-head series 5-1 and has won their past five matches, all in straight sets, including at Wimbledon last year and the Australian Open this year.

Novak Djokovic, meanwhile, turned things around and avoided what would have been his earliest exit at the All England Club since 2016, coming through for a 1-6, 6-4, 6-4, 6-4 victory over 11th-seeded Alex de Minaur at Centre Court.

Djokovic’s bid for an eighth Wimbledon title and 25th Grand Slam singles trophy overall will continue against No. 22 Flavio Cobolli of Italy, who beat 2014 U.S. Open champion Marin Cilic, 6-4, 6-4, 6-7 (4), 7-6 (3).

What else happened at Wimbledon?

No. 7 Mirra Andreeva, an 18-year-old Russian, became the youngest player to reach the women’s quarterfinals at Wimbledon since Nicole Vaidisova in 2007, beating No. 10 Emma Navarro 6-2, 6-3. Andreeva next meets Belinda Bencic, who defeated No. 18 Ekaterina Alexandrova 7-6 (4), 6-4. No. 8 Iga Swiatek was a 6-4, 6-1 winner against No. 23 Clara Tauson and will play No. 19 Liudmila Samsonova.