Djokovic scrapes into semis after Musetti injury

Novak Djokovic's bid to make more tennis history is still alive as he scraped into the Australian Open semi-finals when Lorenzo Musetti retired injured while leading by two sets.

Djokovic, aiming for a standalone record 25th Grand Slam singles title, was wayward, error-strewn and irritable against the inspired Italian in front of a stunned crowd.

Musetti was 6-4 6-3 up and looked set for the semi-finals when he pulled up early in the third set.

The fifth seed took a medical timeout for treatment on his thigh but, unable to serve or move properly, he walked to the net and shook hands at 3-1 down in the third.

A heartbroken Musetti was helped down the corridor by a member of his team as he left the court.

"He was a far better player - I was on my way home tonight," the 38-year-old Serb great said.

"I really wish him a speedy recovery. He should have been a winner today, there's no doubt.

"I am extremely lucky to get through this one today."

Djokovic received treatment for blisters on his feet at the end of the second set and could also have been tested physically had the match continued.

It is another stroke of luck for Djokovic after fourth-round opponent Jakub Mensik withdrew before their scheduled match with injury.

Djokovic has not won a set since his third-round victory over Botic van de Zandschulp on 24 January.

He will need to be at his best in Friday's semi-final against Jannik Sinner, who has won six of their past seven meetings.

Two-time defending champion Sinner had some physical struggles but was good enough to beat Ben Shelton 6-3 6-4 6-4 in the other quarter-final.

For Djokovic to move ahead of Margaret Court's record of 24 major singles titles, he will need to limit his time on court, keep the points short and hope some good fortune goes his way.

He has managed those so far - but he would not have anticipated reaching the semi-finals with such a heavy reliance on fortuity.

Djokovic started sharply against Musetti, going an immediate break up, but then spectacularly lost his way.

A dreadful miss on an overhead handed the break back to Musetti and Djokovic never recovered, sending down just one ace and committing 18 unforced errors to nine winners on his way to losing the first set.

Djokovic frequently turned to his box in disbelief and annoyance - but he only had himself to blame at the start of the second set.

After breaking Musetti and getting out to a 30-0 lead on serve, Djokovic hit five unforced errors in six points to hand the initiative back.

Anchored by a one-handed backhand that kept Djokovic guessing and an improved serve, Musetti held off his opponent to move within touching distance of a first Australian Open semi-final.

Musetti's level just made the injury all the more surprising. After being broken in the third set, he immediately called for the trainer and, after a valiant attempt at his next service game, called it quits.

"I honestly have no words to describe how I'm feeling right now," Musetti said.

"I felt it at the beginning of the second set. I was feeling that the pain was increasing and the problem was not getting away."

Djokovic had warm words for his opponent at the net and afterwards - and, having struggled with physical issues early in his career, would know how devastated the 23-year-old was.

Later on Wednesday, Sinner stormed past Shelton and into his sixth successive Grand Slam semi-final.

Sinner had won his previous eight meetings against the left-handed American without dropping a single set and that trend continued on Rod Laver Arena.

The Italian, who is hoping to win a third straight title in Melbourne, battled 40C heat and cramps in the third round, while he still showed some signs of fatigue in his fourth-round match against fellow Italian Luciano Darderi.

But Sinner looked close to his best in the opening set, hitting 18 winners to just four unforced errors before taking command with an early break in the second set.

He seemed to tire and looked somewhat unsteady on his feet halfway through the third set, but the second seed powered through and struck the decisive blow at 4-4 before serving out the victory.

Despite suffering a brief blip, Sinner said he was feeling "stronger physically" and "moving a little bit better" than he had done in the previous rounds.

Sinner has now won 19 matches in a row at the Australian Open - a record he will hope to extend on Friday when he faces Djokovic.

"These are the moments you practise for, you wake up in the morning and you look forward to playing hopefully a good match," said Sinner, who has beaten Djokovic in their past three Grand Slam meetings.

"You have to play at your best. I'm looking forward to it. But also in the past, I've had great lessons. It doesn't really matter if you win, it improves you as a player and as a person."