Nadal ultimately prevailed at 2:04 a.m., 0-6, 6-4, 7-5, 6-7 (4), 7-6 (5).
These two have faced one another 10 total includes including three times this year, though no previous meetings were during the US Open. 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.
The world number one worked his way back into the match but he was never in control and Thiem served for the third set.
Thiem made his intentions clear after clinching the opening set 6-0 as he made the Spaniard sweat hard to earn points in the quarter-finals clash.
In a rematch of the French Open final, won by Nadal in June, Nadal sealed victory in a tense fifth-set tiebreak as the clock ticked past 2am after a marathon four hours and 49 minutes on court.
"It's going to be stuck in my mind forever..."
Thiem returned the favor, breaking Nadal again to cut the set to 5-4. "Not insane, but tough", Nadal said. It's cruel sometimes tennis, because I think this match didn't really deserve a loser. It was a very tough start for me.
Elon Musk on Joe Rogan Experience
Bloomberg also reported Tesla's chief people officer Gaby Toledano would not return from a holiday just over a year after joining. He took leave from the company in 2015 but rejoined to work on the Semi truck revealed in November of previous year .
Two Injured, Three Killed in Cincinnati Bank Shooting
Bank employees sheltered in situ for an hour or more as officers swept the building and cordoned off several downtown city blocks. The Hamilton County Coroner's office identified the victims as Pruthvi Kandepi, 25; Luis Calderon, 48; and Richard Newcomer, 64.
Turkey proposing to evacuate Syrian rebels from Idlib, says report
Iran's president is hosting his Russian and Turkish counterparts for a summit on the Syrian war. A general view taken with a drone shows part of the rebel-held Idlib city, Syria, June 8, 2017.
Nadal was clearly rattled and lost the first three points of the tiebreak that Thiem won 7-4 to force a fourth set.
Nadal's ability to look only forward and forget what went before is one of his most important strengths and he set about turning around the match, closing in on the baseline, forcing Thiem to play one more ball and, eventually, to go for too much. But once again Nadal stepped up the level, saved two break points in the game and then went on to claw back to 4-4.
But he took the tiebreaker before Nadal just proved the steadier of the two in the final set decider. Thiem is a top-10 player himself (he's now ranked No. 9), a star in his own right who some consider to be the heir apparent to Nadal.
Each player held serve in the second set until Nadal earned his first break in the eighth game to take a 5-3 lead.
"Whatever the humidity is on outer courts or in the city, I think it's amplified on centre court", Isner said. Of course, now I'm devastated a little bit. I fought until the end. Defending champion Stephens is up first on Arthur Ashe Stadium, facing No. 19 seed Anastasija Sevastova in a rematch of Stephens' three-set victory in the same round at Flushing Meadows a year ago.
When it was all over, Nadal was happy to be in a seventh US Open semifinal, but even happier that he'd done everything he could to turn the match around. "Beating John in these kind of matches is like an epic, an epic match".