Nadal 'destroyed physically' by epic Shapovalov win to reach semis
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But the Spanish great still managed to move to within two matches of a record 21st Grand Slam title with an incredible display of guts and resilience against the talented 22-year-old.
The sixth seed edged the Canadian 14th seed 6-3, 6-4, 4-6, 3-6, 6-3 in 4hr 8min of thrilling action on Rod Laver Arena.
"I was honestly destroyed physically. But my serve worked well, and for me, every game that I was winning with my serve was a victory," said Nadal, who will have two days to recuperate before Friday's semi-finals.
"Being in semi-finals means a lot to me and to have a victory against a great player after all the things that I went through, so it's an amazing news. I'm super happy."
It will be Nadal's seventh semi-final in Melbourne where he will meet either Matteo Berrettini or Gael Monfils.
Nadal is tied with great rivals Novak Djokovic and Roger Federer on 20 Grand Slams, but with Djokovic deported and Federer injured, the opportunity is there for him to go clear at the top.
Nadal said he was not consumed by going after the record.
"For me, the fact that we are equal at 20, it's just the only thing that says we share an amazing part of the history of our sport, and for me it's a real honour to be part of it," he said.
"Let's enjoy the situation that we did, every one of us, we did very special things in our sport.
"Let's enjoy that. Doesn't matter the other thing."
He raced into a two-set lead but was visibly hampered by stomach issues before eventually coming through after a spirited fightback from Shapovalov peppered with winners to all parts of the court.
"I started to feel not well in my stomach. They checked everything was all right with my body," said Nadal, who received medical attention in the fourth set.
"I took some tablets to try and improve my stomach."
Nadal looked on course for a routine straight sets win before Shapovalov hit back to take the quarter-final into a thrilling deciding-set climax.
The Spaniard broke in Shapovalov's opening service game and held on to take the victory.
The feisty Canadian, who was coming off a straight-sets upset of third seed Alexander Zverev, slammed his racquet into the court in anger at losing the epic battle.
There was a testy exchange early in the second set with Shapovalov heard to accuse chair umpire Carlos Bernardes of being "corrupt."
Nadal has a reputation of taking his time between serves right up to the final second of the shot clock and Shapovalov believed the Spaniard deserved a time violation.
In response to Shapovalov's post-match gripes that he gets preferential treatment because of who he is, Nadal said: "Not in that case, no, no.
"I really believe that on the court you don't deserve better treatment than the others. And I really don't want it and I don't feel I have it."