LONDON — Jannik Sinner progressed to the Wimbledon quarterfinals on Monday after a tearful Grigor Dimitrov pulled out injured while in total control of their fourth-round match, as Novak Djokovic, meanwhile, survived a scare to advance.

World No 1 Sinner and seven-time champion Djokovic remain on course for a mouthwatering semifinal clash, but at the cost of Dimitrov's heartbreak, which overshadowed the top seed's match on Centre Court.

The Italian was staring at the exit door, trailing 3-6, 5-7, 2-2, before the Bulgarian 19th seed pulled up holding his right pectoral muscle and was unable to continue.

Sinner rushed to his aid, but his 34-year-old opponent was barely able to wave to acknowledge the crowd's warm ovation.

"Honestly, I don't know what to say," said Sinner. "He is an incredible player, I think we all saw this today.

"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.

"Seeing him in this position, honestly, if there would be a chance that he could play the next round, he would deserve it."

The injury-prone Dimitrov has now been forced to retire from each of the past five Grand Slams he's started.

Sinner himself suffered a nasty fall in the opening game of the fourth-round clash, and appeared to be suffering discomfort in his right elbow.

The three-time Grand Slam champion had been in regal form in the first three rounds at the All England Club, dropping just 17 games.

Sinner, who is due to face American 10th seed Ben Shelton in the quarterfinals, said he would be having an MRI scan on Tuesday to assess the extent of the damage to his elbow.

Shelton beat Italy's Lorenzo Sonego in four sets.