Lorenzo Musetti had Novak Djokovic at his mercy.
Fashioning a formidable two-sets-to-love buffer on Wednesday after having conjured five service breaks, Musetti was on a swift path to adding an Australian Open semifinal berth to his collection, joining his final-four appearances at Wimbledon and Roland Garros.
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Djokovic was powerless to stop Musetti, who looked set to replicate his straight-sets, fourth-round dismissal of Taylor Fritz two days previously.
In the end, the only thing that could possibly stop Musetti was Musetti's own body.
The No.5 seed felt a tweak in his upper right leg at the beginning of the second set, which descended into a suspected torn adductor in the aborted third set.
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Down 1-3, Musetti tamely double-faulted for 15-40 before forlornly clasping his hand to his face, sliding off his headband and making the slow walk to the net to concede defeat to a man he had spent most of the previous 128 minutes completely outgunning.
"I felt it at the beginning of the second set," Musetti said. "I felt there was something strange in my right leg.
"I continued to play, because I was playing really, really, really well, but I was feeling that the pain was increasing, and the problem was not getting away."
Musetti's movement looked shot as he gave up to concede the third game of the third set before he immediately sought treatment.
"At the end, when I took the medical time-out, to stay three minutes, I sat, and when I started to play again, I felt even more and was getting higher and higher the level of the pain," Musetti said.
"I'm not doctor, but it's kind of on the … I don't know if it's the adductor or... I don't know. But, of course, I will do all the exams when I come back home."
A dampened sense of heartbreak enveloped Rod Laver Arena given how brilliantly the 23-year-old Italian had been playing. His defence had been stellar, his offence sizzling.
Djokovic, after a promising 2-0 start, found himself being battered from the baseline. Errors mounted off his racquet, and his serve-volleying variations proved only moderately fruitful.
In addition to a red-lining opponent, Djokovic was also grappling with a nasty foot blister, which required re-taping during a medical time-out of his own at the end of the second set.
Musetti stayed in his own bubble in that moment, more concerned with his own body which was slowly betraying him.
"I saw that he got the medical timeout, but I was not really worried about him," he said with a smile.
Musetti's 1-10 record against Djokovic doesn't tell the true tale of this head-to-head.
At Roland Garros in 2021, a teenaged Musetti went up two sets against world No.1 Djokovic before eventually retiring in the fifth with a lower back injury.
Three years later on that same patch of red dirt in Paris, he pushed defending champion Djokovic to five again.
At last year's French Open, Musetti was playing the match of his life, snatching the first set off Carlos Alcaraz before retiring in the fourth set when he injured his right groin.
As disappointing as he felt after having to concede to Alcaraz last May, that doesn't compare to his level of devastation on Wednesday.
"Well, definitely yes," he responded when asked whether this was the hardest loss he has ever had to swallow.
"Honestly, I never imagined the feeling of leading two sets to zero against Novak and playing like that, having the lead of the match like that and being forced to retire.
"It's something that, of course, I will never imagine. Of course, it's really painful."