Novak Djokovic continued his quest for a record-extending 11th Australian Open title and standalone 25th Grand Slam crown, but only after a cruel twist of fate for Lorenzo Musetti, who quit their quarterfinal due to injury on Wednesday holding a comfortable lead.
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While the stars may seem to be aligning for Djokovic in his bid for more major glory, the road will only be more rocky after Jannik Sinner beat Ben Shelton to book a blockbuster semifinal against him, and Carlos Alcaraz potentially in the final.
Like Alcaraz, Iga Swiatek arrived in Melbourne chasing a career Grand Slam - the feat of winning all four of the sport's biggest trophies - but her bid went up in smoke after a defeat by Elena Rybakina earlier in the day.
Jessica Pegula had little trouble as she reached the Melbourne Park semifinals for the first time after dashing fellow American Amanda Anisimova's hopes of reaching three straight major finals.
The drama in the day session was reserved for the afternoon match and Djokovic arrived fresh for the battle with fifth seed Musetti after getting a walkover on Sunday from injured Czech Jakub Mensik.
The Serb made a fast start but it was then one-way traffic as the artistic Musetti showed his full range of strokes and bagged the opening two sets, before the Italian pulled up holding the upper part of his right leg at the start of the third.
Musetti looked to soldier on after receiving treatment, but lasted only one more game and he threw in the towel while leading 6-4 6-3 1-3 as stunned fans at the Rod Laver Arena let out a gasp and Djokovic quietly heaved a sigh of relief.
"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. These things happen in sport and it's happened to me a few times, but being in the quarterfinals of a Grand Slam, two sets to love up and being in full control, I mean it's so unfortunate."
'SOMETHING STRANGE'
A heartbroken Musetti said he was pained by having to retire after taking a big lead against the experienced Djokovic, adding the trouble in his leg first began in the second set.
"I felt there was something strange," he said.
"I continued to play, because I was playing really well, but I was feeling that the pain was increasing, and the problem was not going away.
"In the end, when I took the medical timeout ... and started to play again, I felt it even more and it was getting higher and higher, the level of the pain."
Although he eclipsed Roger Federer with his 103rd match win at Melbourne Park, the task will get only tougher for Djokovic when he meets Sinner, who won a 22nd consecutive set against Shelton in a 6-3 6-4 6-4 victory in the evening session.
Djokovic admitted that Sinner was the "absolute favourite".
"You never know," he said. "Hopefully, I can deliver my A-game for that match, because that's what's going to be needed at least to have a chance.
"I wasn't playing close to my best today, so I'm going to have to change that around."
DOMINANT DISPLAY
As one fifth seed crashed, another advanced as Elena Rybakina booked her place in the semifinals with a dominant 7-5 6-1 win over six-time Grand Slam champion Swiatek.
The Pole was left to rue the defeat and the lack of privacy in difficult moments off the court where players cannot escape cameras, a day after Coco Gauff's racket-smashing meltdown in response to her defeat by Elina Svitolina.
"The question is, are we tennis players or are we animals in the zoo, where they are observed even when they poop?" she said.
"That was exaggerating obviously, but it would be nice to have privacy. It would be nice also to have your own process and not always be observed."
All eyes were on sixth seed Pegula as she stayed on course for her maiden Grand Slam trophy by beating Anisimova 6-2 7-6(1), sparkling despite testing moments towards the end of the clash.
"I'm really happy with my performance," Pegula said.
"From start to finish, there was a lot of momentum swings, but I thought I came out playing really well, and was able to just hold on there in the second and get that break back and take it in two. I showed good mental resilience there at the end not to get frustrated."