There was nothing left to give and, when a sprayed overhead smash from Thiem sealed Nadal's epic 0-6 6-4 7-5 6-7 (4-7) 7-6 (7-5) US Open quarter-final victor on Wednesday, Nadal's reaction spoke volumes of his character.
Rafael Nadal began his U.S. Open quarterfinal as poorly as possible, shut out in a set by a 6-0 score for only the fourth time in 282 career Grand Slam matches.
After Nadal roared back to take a 2-1 lead, the fourth set went to a tiebreak.
"I suffered, that's the right word", said Nadal after playing his longest ever match at the tournament.
"It's been a great battle, the conditions were tough, a lot of humidity".
"In the first set I only won seven points, I hadn't started and it could've been very unpleasant".
The victory, which puts the defending champion through to his third consecutive Grand Slam semifinal, came hours after Williams booked her 12th U.S. Open semifinal and the night after Roger Federer was ousted by the unseeded Australian John Millman in the fourth round.
"He is a very well educated guy and a top person".
Going into the match, Thiem held a 3-7 win-loss record over Nadal.
By virtue of losing the opening set against John Isner, Del Potro ensured the US Open will remain the only grand slam in the Open era where no man has won the singles title without dropping a set.
The Spaniard was able to bounce back and win the next two sets 6-4, 7-5, but not without a fight from Thiem.
"I am the guy to look at myself", Nadal said.
Nadal said he had told Thiem he was sorry for the result although the Austrian laughed off that consolation from his close friend. "I mean, it's cruel sometimes tennis, you know, because I think this match didn't really deserve a loser".
"To reach the semifinal again here in NY in my favourite tournament is very special to me", said Del Potro after his eighth win over Isner in 12 meetings.
Nadal trailed by a break in the third set before taking it. "I hope that we have many more in the future with a different end".
Breaking Thiem at a crucial juncture, the World No.1 quickly closed out the set but then found himself in trouble early on in the second.
There were no breaks of serve in the deciding set and a second tiebreak ensued.
"It's going to be stuck in my mind forever..."
Del Potro admitted the 33-degree temperatures proved a real challenge with the 10-minute heat rule allowing the players a welcome respite after the third set. "It's good to have now two days [without a match] that probably give me the chance to be 100 per cent in the semi-finals". The giant American was presented with the US Open sportsmanship award following the quarter-final to recognise his conduct during the tournament and the warm-up events.
It was the first still moment in almost five hours of epic, smash-ball, anything-you-can-hit-I-can-hit-harder tennis.