Musetti’s retirement when leading 6-4, 6-3, 1-3 meant Djokovic pulled off a great escape at his most successful hunting ground, with the 10-times champion’s bid for a standalone 25th major to break the tie with Margaret Court still alive.

“I don’t know what to say, except that I feel really sorry for him and he was a far better player,” Djokovic said.

“I was on my way home tonight. These things happen in sport, and it’s happened to me a few times, but being in the quarter-finals of a Grand Slam, two sets to love up and being in full control, I mean, it’s so unfortunate.

“I wish him a speedy recovery, and he should have been the winner today, there’s no doubt.”

The 38-year-old Serb returned to action after an extended break following fourth-round opponent Jakub Mensik’s walkover on Sunday, and his freshness showed during a sharp start where he brought plenty of variety and grabbed an early break.

But some loose points thereafter allowed Musetti to level at 2-2, and the Italian then surged past Djokovic for the first time in the contest with an overhead shot before comfortably wrapping up the opening set on serve.

“My strategy worked very well for the first couple of games, and then it changed completely,” Djokovic said.

“I had four winners in the first two games and no unforced errors, and then the rest of the match I had another four winners and probably 40 errors. That’s what Lorenzo does to you, makes you play when you think the point is finished.

“When you attack him, you don’t know what to expect, whether it’s going to be a passing shot, a crosscourt or a short slice, or if he’s going to go full flat in your body or hit a looping ball to my weakest shot, which is overhead.

“I tried my best … I wasn’t feeling the ball today, the first couple of sets, but that’s also due to his quality and his variety in the game. I’m fortunate to get through this one.”

Fiery winners from both flanks helped Musetti break in the opening game of the next set, and though the 23-year-old let the advantage slip immediately, he edged in front again and soon doubled his lead in the match, to leave Djokovic on the ropes.

Djokovic soldiered on following treatment for a foot blister and went 2-1 up with a break in the third, when it was Musetti’s turn to call the trainer to the court for what appeared like a right thigh issue.

Musetti looked to manage the problem and play on, but he was far from 100% and threw in the towel a game later to gasps from the Rod Laver Arena crowd, handing Djokovic his 103rd match win at the tournament to eclipse Roger Federer’s mark.

Djokovic faces the winner of the quarter-final between defending champion Jannik Sinner and Ben Shelton.

“I’m going to double my prayers tonight, for sure, and show gratitude to God for giving me this opportunity,” Djokovic said.

“I’m going to do my best in a couple of days to use it … Today I wasn’t happy with my performance, but it’s another day in the office, and hopefully in a couple of days, I can come out and be at my best, because that’s what’s needed.”