The 2009 champion who will next face Roger Federer, saved two match points in the fourth set of what was arguably the best of the tournament so far.
An ailing Juan Martin Del Potro came back from the brink of defeat to beat Austrian sixth seed Dominic Thiem 1-6, 2-6, 6-1, 7-6(1), 6-4 and reach the last eight of the US Open on Monday.
Del Potro, the 2009 champion who will next face Roger Federer, saved two match points in the fourth set of what was arguably the best of the tournament so far.
“Oh my God, I don’t know (I won). What can I say after a battle like this. I was sick the last two days and I just tried to improve game after game,” 24th seed Del Potro, who took a pill near the end of the opening set, said on court.
"I fought like this because of you guys, so thank you very much,” he added in reference to the noisy Argentine fans who had turned the Grandstand Arena into a raucous soccer-stadium like atmosphere.
"The crowd was on his side. But it was a great atmosphere,” said Thiem. “I mean, we’re not playing every day in an atmosphere like this.”
Del Potro struggled early on, spraying the court with unforced errors and the Argentine called the doctor twice.
At 5-0, he took a tablet. He won one game and had two break points at 5-1 but Thiem, who was looking to book his spot in the last eight here for the first time, coolly closed out the set.
He raced to a 4-0 lead in the second as Del Potro looked completely out of sorts.
The ‘Dominator’ was in full control, dictating the play with deep forehands, and he sealed the set with a cracking backhand winner down the line.
The question was then whether Del Potro would retire.
But the Argentine found his range with his impressive wristy forehand. His opponent could not keep up the pace and Del Potro easily pulled one back.
The real fight started in the fourth set.
Del Potro broke for 2-1 but Thiem played tighter and broke immediately back. A delightful backhand winner earned him another break for 4-2 and the Austrian served for the set at 5-3.
He led 30-0 but lost his focus and scooped a forehand long to allow Del Potro back in the contest.
Thiem had two match points at 6-5 but Del Potro saved them with consecutive aces -- one of them at 204 kph.
In the resulting tiebreak, Thiem suffered a meltdown and Del Potro levelled with a gravity-defying crosscourt forehand winner.
The decider was tightly contested but Del Potro eventually had the last word. On the second match point, he challenged Thiem’s second serve and was spot on as the ball was out, meaning the wiry Argentine got to fight another day.
Federer eases into quarters
Roger Federer crushed Germany’s Philipp Kohlschreiber 6-4, 6-2, 7-5 to ease into the quarter-finals of the US Open.
Unbeaten by the German in 11 matches prior to Monday’s clash, Federer started quietly and was content to feel out his opponent but it was not long until he turned up the pressure and broke his opponent with a thundering forehand before wrapping up the first set.
With the match on serve at 2-1, razor sharp Federer tore through six successive games to take the second set and go 1-0 up in the third.
With Kohlschreiber on the ropes, the 36-year-old Swiss seemed to ease up but he took the decisive break at 6-5 before closing out the match with a classic forehand winner.
If there was one worry about the Swiss in the one-sided contest, it was the sight of him leaving the court before the start of the third set to receive treatment on a back that had given him problems in the run-up to the grand slam.
Federer, however, downplayed the timeout, declaring himself 100 percent healthy and ready to go.
"I just felt something, sort of my muscle being tight at the back," explained Federer. "I just wanted to get it done really quickly after the set break."
"It was more precaution. It’s all good. No problems there. I‘m not worried about it."
Keys makes it four for American women at US Open
Madison Keys took advantage of Elina Svitolina's nerves to reach the US Open quarter-finals for the first time with a 7-6(2), 1-6, 6-4 win on Monday, meaning four American women are still in contention -- a first since 2002.
The 15th-seeded Keys was down a break in the decider against the Ukrainian fourth seed when Svitolina lost her composure and allowed the Florida-based player to come back under the lights on Arthur Ashe Stadium.
"It's gone pretty well so far don't you think," she said on court.
"It's partially thanks to you guys, you helped me when I got down in the third set; You gave me an amazing energy boost."
The last time at least four American women were in the quarter finals at Flushing Meadows was in 2002, with Jennifer Capriati, Lindsay Davenport, Serena and Venus Williams and Monica Seles winning their fourth-round matches.
Jennifer Brady could have been the fifth this year but she was destroyed 6-1, 6-0 by world number one Karolina Pliskova earlier on Monday.
Keys joined Coco Vandeweghe, who will meet Pliskova in the last eight, Sloane Stephens and Venus.
Davenport is now Keys's coach and she was seen crying in the stands after her protege hit a backhand winner down the line to seal the victory.
Keys got off to a nervous start as she quickly fell 3-0 behind but once she found her stride, Svitolina was on the back foot and the American forced a tiebreak which she easily won after earning a mini-break with a superb drop volley.
More at ease in the long rallies, Keys was, however, completely overpowered by the big-hitting Svitolina in the second set and the Ukrainian took that momentum into the third.
"I had the feeling I was hitting a wall in the second set," said Keys.
Svitolina broke for 3-2 and held for 4-2 when her nerves got the best of her.