Unseeded Michelsen came into the match in fine form, having not dropped a set at the tournament prior to facing Tiafoe, and grasped the momentum in the first set.
After the pair traded breaks of serve early in the match, Michelsen got the deciding break at 6-5 in a set where he fired 15 winners to Tiafoe’s four.
Michelsen continued to have the upper hand, with his backhand proving decisive on key points and, after taking the second set, he went up a break early in the third.
It was not until Michelsen was serving for the match at 5-4 that nerves began to hit. He served two double faults and Tiafoe broke to level, won the set and took the opening three games of the fourth set.
After holding Michelsen off, Tiafoe took the match to a deciding set where the pair traded multiple breaks of serve – invigorating the spectators on Arthur Ashe Stadium.
A fan favourite, Tiafoe thrived off the energy of the New York crowd as he then got the better of the tie-break to seal his fourth five-set victory at a major in 2026.
“He’s a great guy for consoling me in that moment,” said Michelsen of their post-match embrace.
“I was trying to keep it together, and I didn’t do a good job of that. He was saying a lot of nice personal things.
“I’ve got a lot of time to grow physically and mentally. I’m going to be here again. I know it.”
Tiafoe is hoping to reach the final at Flushing Meadows for the first time, following defeats by Alcaraz in 2022 and Taylor Fritz in 2024.