NEW YORK (AFP) - Juan Martin del Potro reached the US Open semi-finals for the third time on Tuesday (Sept 4), defeating John Isner 6-7 (5-7), 6-3, 7-6 (7-4), 6-2 and ending American hopes of a first men's champion at the event since 2003.
Argentinian third seed del Potro, the winner in 2009, goes on to face defending champion Rafael Nadal, who overcame Austria's Dominic Thiem in a five-setter, for a place in the final.
Del Potro dropped his first set of the tournament against 11th seed Isner, who was playing in his maiden quarter-final at his home Slam.
Despite that, the 29-year-old was never broken in the 3hr 31min match, where Isner unleashed 26 aces but was undone by his 52 unforced errors compared to del Potro's 14.
But it was his and del Potro's struggles with the heat which dominated conversation, after the gruelling match on the same Arthur Ashe Stadium which had witnessed the demise of Roger Federer the previous evening.
With the extreme heat rule allowing for a 10-minute respite between the third and fourth sets, both men took full advantage.
"I had to change my shirt 11 times in the match," said Isner. "I weigh 238 pounds (108kg), so I have always said it's pretty difficult to play in hot conditions, for me especially, because I weigh a lot and I sweat a lot.
"It takes its toll on bigger guys. Whenever I have seen Juan maybe struggle in the heat or on TV and it looks like he's gassed out there, I can always relate."
Federer complained that he had struggled to breathe in the almost airless conditions inside the arena as he slumped to a shock defeat by John Millman, the world No. 55 on Monday.
"I have never seen Roger sweat ever. If he's sweating a lot and has to change clothes, then you know it's pretty humid out there," said Isner.