Still, del Potro never gave in or gave up, eventually working his way all the way back on the strength of powerful serves and thunderous forehands to edge Thiem 1-6, 2-6, 6-1, 7-6 (7-1), 6-4 over more than three and a half hours and set up a quarter-final showdown against Roger Federer.

“Thanks so much for all the support you gave,” Del Potro told the boisterous Grandstand crowd that regaled the Argentine with “Ole!” chants. “It helped me a lot. ... I won’t forget this match.”

Thiem also aided 24th seed Del Potro by playing his worst tennis when he was closest to victory in the fourth set, which he led 5-2.

The Austrian served for the match at 5-3, but got broken. Leading 6-5, he managed to get within a point of winning at 15-40 on Del Potro’s serve, but a pair of aces at 127mph and 121mph erased those two chances.

The ensuing tiebreaker was dominated by Del Potro, who closed it with a booming cross-court forehand winner on the run.

In the fifth set, Del Potro closed things on his second match point, when Thiem double-faulted. How close was this? Thiem actually won more points, 141-139.

When it was over, del Potro raised both arms overhead and threw his head back, enjoying the fans’ adulation, then crossed himself.

He joked that he thought he should get a trophy just for winning this one.

It was by far the day’s most enthralling match, with spectators’ roars heard all the way across the grounds at Arthur Ashe Stadium, where Federer was beating world No 33 Philipp Kohlschreiber 6-4, 6-2, 7-5.

The only bit of intrigue came after the second set, when Federer left to take a medical timeout. He said afterward with a laugh that it was so he could get “a bit of a rub on my back – or my bottom – and I didn’t want to do it on court”.

His back had been bothering Federer before the US Open and restricted his practice time, something he blamed for problems while getting pushed to five sets in each of the first two rounds last week.

But the lopsided win against Kohlschreiber – who never held a break point – was Federer’s second in a row in straight sets.

Federer improved to 12-0 against Kohlschreiber; his record against Del Potro is 16-5. But del Potro won their meeting in the 2009 final in New York in five sets for his only grand slam title, ending Federer’s streak of five straight US Open championships – and he has not won the trophy since.

The other match-up on that half of the men’s bracket will be world No 1 Rafael Nadal against 19-year-old Andrey Rublev, the youngest quarter-finalist at the US Open since Andy Roddick was 19 in 2001.

Nadal got to the round of eight in New York for the first time since his 2013 title, overwhelming world No 64 Alexandr Dolgopolov 6-2, 6-4, 6-1.

“Every victory, every set that you win, is more confidence,” Nadal said. “That what’s I am doing.”

Dolgopolov, who has been interviewed by anti-corruption investigators about a match with unusual betting patterns last month at another tournament, was hesitant to give Nadal too much credit.

“I was just feeling flat,” Dolgopolov said. “I don’t know why.”

Now Nadal gets to play a fifth consecutive unseeded foe in Rublev, who took out No 9 David Goffin 7-5, 7-6 (7-5), 6-3.

The top-seeded woman had even less trouble than Nadal did: 2016 runner-up Karolina Pliskova beat world No 91 American Jennifer Brady 6-1, 6-0.

In the quarter-finals, Pliskova will take on No 20 Coco Vandeweghe, who beat Lucie Safarova 6-4, 7-6 to become the third US woman in the next round.

Venus Williams and Sloane Stephens advanced on Sunday.

There was a chance for a fourth American to join them, because 15th seed Madison Keys was expected to play the last match against No 4 Elina Svitolina of Ukraine.

That winner faces Estonia’s Kaia Kanepi, who beat Daria Kasatkina 6-4, 6-4 to become the first qualifier in 36 years to reach the US Open women’s quarter-finals.