Andy Murray, with Ricky Hatton in the stands, outfought and out-thought Rafael Nadal, who limped out of their Australian Open quarter-final, trailing 3-6, 6-7 (2-7), 0-3 and with his chronically troubled knee throbbing painfully.
"I'm so sorry," Murray said to his Spanish friend when they called it off in the third set. The injury throws Nadal's glorious career into doubt. But Murray was winning strongly in one of the best contests at the Rod Laver Arena in this tournament.
Murray meets the Croatian Maric Cilic in the semi-final on Thursday and, in all probability, Roger Federer in the final on Sunday.
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If the 22-year-old Scot wins, he will become the first British male to win a major since Fred Perry's last Wimbledon in 1936 – a statistic British tennis fans have long wearied of thinking about.
But that is what is riding on Murray's final two games in Melbourne. On this showing, he is in great shape to make history. John Lloyd was the last Briton to reach a final here, in 1977.
"I hope I'm going to turn that around," Murray said of the rematch with Cilic, who beat him in the US Open (not one of Murray's best showings). "I'm feeling good here, so I think I've got a good shot."
He was strong in every department, from his rocket-like first serve to the brilliance of his strategy. He came to the net behind his serve deeper into the match after a cautious start and had Nadal stretched in almost every game.
It might have gone either way in the first set, as both players struggled to hold serve. When Murray outlasted Nadal in the second-set tie-break, though, the momentum was firmly with him.
Nadal was a forlorn figure at the start of the third set, receiving a massage to his right knee. He battled on for a little while longer, like all brave fighters – but there was no point carrying on when he'd gone 3-0 down.