Novak Djokovic admitted he thought he was on his way home before being handed an Australian Open reprieve when quarter-final opponent Lorenzo Musetti retired injured. Musetti looked well on course to beat Djokovic after racing into a 6-4 6-3 lead after two hours of play.

However, disaster soon struck for Musetti when he appeared to tweak a leg muscle in his opening game of the third. And after going 3-1 down in the third set, Musetti retired, shaking hands with Djokovic at the net.

The Serbian, who was forced out of last year's semi-final here through injury, looked stunned before admitting he was extremely fortunate. He said: "I don't know what to say except that I feel really sorry for him.

"He was the far better player, I was on my way home. It happened to me a few times, but being in the quarters of a slam, two sets to love up, in full control, so unfortunate. I wish him a speedy recovery and he should have been the winner today, no doubt.

"I'm going to double my prayers tonight of gratitude to the God for really giving me the opportunity. I'm going to do my best in a couple of days to use it."

Djokovic was unable to find anything like his best level, making 32 unforced errors. He also received medical treatment during the game but revealed afterwards the treatment was for a large blister.

"A blister here and there but nothing major," he said. "I wasn't feeling the ball today and that was due to his quality and variety in the game. I am just extremely lucky to get through this one today."

On his performance, the 38-year-old said: "The strategy worked well for the first couple of games, but then it changed. Completely. I had four winners in the first two games and no unforced errors. Then the rest of the match I had another four winners and probably 40 errors.

"That's what Lorenzo does to you, he makes you play. When you think the point is finished, it's not. When you attack him, you don't know what to expect.

"Whether it's going to be a passing shot, cross-court, or short slice or full flat in the body, or just a looping ball to my weakest shot, which is overhead. I think we saw that again today. What can I say? I tried my best. I can't complain."

Djokovic will play either Jannik Sinner or Ben Shelton in the semi-finals, but the No.4 seed knows he must improve. He said: "I will watch the match [between Sinner and Shelton]. I will watch my match with my team and try to get some insight into both these guys' game.

"But my main priority remains my game, I played really well until today throughout the whole tournament. Today I am definitely not happy with my performance, but it's another day in the office and hopefully in another day's time I can be at my best because that's what's going to be needed."