US Open: Juan Martin del Potro thanks crowd for epic win, sets up last-eight showdown with Roger Federer

Juan Martin del Potro produced a stunning comeback to reach the US Open quarter-finals on Monday, a feat he believes was impossible without the backing of a partisan crowd.

The Argentine, who lifted the trophy in New York in 2009, has been a Flushing Meadows favourite and needed all the support he could get against Austrian sixth seed Dominic Thiem.

"I'm getting good energy from the crowd in every match," he had said before his 1-6, 2-6, 6-1, 7-6, 6-4 win on Grandstand court.

The 24th seed, whose career has been plagued by multiple injuries, said he was about to retire when he drew some energy from the crowd as Thiem was cruising to victory.

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"I was thinking to retire in the middle of the second set because I couldn't breathe, I couldn't move well," said Del Potro, who called the doctor twice during the opening set.

"Dominic was dominating the match so easy."

Del Potro started to play better, and a break early in the third set gave him the extra confidence he needed to believe in his chances.

"Then when we started the third set, I broke his serve very quickly, and then I won the set in 20 minutes," he said.

"Then it was another story. I started to see the crowd. I took all the energy from the fans. That's what I did and in the end, I just kept fighting. I didn't give up any point from the third until the fifth set."

Del Potro benefited from some Thiem meltdown to take the fourth set in a tiebreak after saving a couple of match points with two aces.

But it was also his flat forehand, one of the best on the tour, that made the difference.

"I know people like when I hit hard with my forehands. People stand up from their chair when I hit good winners," said Del Potro.

"I like to do that. But it doesn't happen very often. When I feel that confidence to do my best shots, I know I can be dangerous for all the guys."

Next up for Del Potro is Swiss Roger Federer, whom he beat in the final here in 2009.

Federer, the third seed, eased into the last-eight with a 6-4, 6-2, 7-5 win over Philipp Kohlschreiber, taking his record over the German veteran to 12-0.

Eight years after losing to Del Potro in the Flushing Meadows final, Federer locks horns again with the giant Argentine in New York still convinced he should have won the match which ended his five-year reign as champion.

Del Potro was just 20 when he downed the Swiss legend 3-6, 7-6, 4-6, 7-6, 6-2 but Federer believes that he was the dominant force in that 2009 showdown.

"The only time when he was really better, in my opinion, was the fifth set. Obviously that was good enough to beat me that day," Federer said.

"I felt like that I left that match with a lot of regrets. Probably feels like one of those matches I would like to play over again.

"Feel like I would probably win it somehow because I should have been up maybe two sets to love."

Federer leads Del Potro 16-5 in their head-to-head record although his win in Miami this year represented the first time the pair had met in four years.