When it was finally over after 2 a.m. ET on Wednesday morning, Nadal and Thiem, clearly exhausted, walked over to each other for a hug, some words and a touching moment of class and sportsmanship at the net.
Thiem became the first player since Andy Roddick in 2004 to win a love set against Nadal in NY but the Spaniard once again dug deep to come out on top of a gruelling battle played in more punishing humidity.
However, the 32-year-old was fortunate to triumph on another hot and humid night at Flushing Meadows, 24 hours after Roger Federer had been dumped out of the tournament by John Millman. He has now won seven U.S. Open quarterfinals in a row when he's made it that far; his only loss in that round came back in 2006. He also has wins over the Austrian at all three of the clay court Masters, including in the final in Madrid a year ago. After that first set, then the match became more normal. "But in some way, being honest, I had a very tough injury in 2005". The Austrian blasted 13 winners, made only two unforced errors and allowed Nadal just seven points in winning an extraordinary opening set. It means a lot to me.
Nadal said that losing the first set by 6-0 was not in his plan but he accepted it with "humility", while in the fifth he had "more options" than Thiem.
Thiem told a post-match media conference: "It's going to be stuck in my mind forever".
The semi-final will pit Nadal against third seed Juan Martin del Potro for the second successive Grand Slam.
But at one point, the 2016 Olympic Games star looked tense as she stood up to applaud her beau.
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Teams with players who do not stand will be subject to fines and teams could also discipline the offenders. The rule also dictates that players who choose to be on the field for the anthem must stand.
The final result was 0-6, 6-4, 7-5, 6 (4) -7 and 7-6 (5) in 4 hours and 49 minutes, which is the longest match of this edition of the tournament.
"If we skip the first set, it was a really open match from beginning to the end". The fourth was a wild 81-minute ride that began with Thiem facing break points, saw the Austrian threaten a double break before being pegged back and then a tired Nadal miss a chance to win the match.
"You are very good", Nadal said. "But I don't play dropshots when I see the player struggling or bending over, no", Sevastova said. "I'm going to remember this match, for sure", Thiem said.
His victory against the world number one in the Madrid semi-finals ended Nadal´s 50-set clay win streak which began after the Austrian had beaten him in Rome 12 months earlier.
"To play John in these kind of matches, it's like an epic". I know how he plays, he knows how I am playing.
There are no chill Rafael Nadal matches, like oh cool, I'll watch some tennis and my blood pressure will stay level.
He then rallied past Taylor Fritz 3-6 6-3 7-6 6-4 before beating 2017 finalist Kevin Anderson in straight sets 7-5 6-2 7-6.
Nadal seemed to be on the verge of cracking the code when he broke back in the fourth and came within two points of winning the match.