By then, Tsitsipas was hobbling badly between points and was in no shape to continue the struggle.
Thiem follows Stefanos Tsitsipas in making an early exit, the 8th seed has lost in four sets to Russian Andrey Rublev. "But it was not the real me there on the court", said Thiem, who prior to the tournament downplayed his chances because of a virus he picked up in the build-up to the last major of 2019. I feel very sorry for him. I don't feel inspired. "He (Millman) showed a year ago what he's able to do when he's doing well and I came on court with a lot of respect", he added.
Tsitsipas stopped short of calling it a factor in his loss but said he felt the impact. He was a fresh-faced, newly minted Next Gen champ in January with a social media account that gave ample measure of his Greek philosophising.
But the Greek, who has a one-handed backhand, seemed mostly unbothered when play resumed but was unable to slow down an in-form Rublev. It's a daily grind, a continuous, seemingly never-ending, process of getting better.
The wiry Russian had his own Grand Slam breakthrough in NY two years ago, when he punched his way to the quarter-finals.
The 21-year-old Russian, who sealed victory in three hours and 56 minutes, will face Gilles Simon in the second round. But a lower back stress fracture last year and a wrist injury earlier this year had stalled his progress. It was Federer's quickest defeat in 16 years. He cracked 51 winners and had 45 unforced errors to his name.
The eighth seed, who battled leg cramps during the final set, got what he asked for and given it was his second time violation of the match, it came with a point penalty. He was penalised for a coaching violation, and later a time violation, and was overheard saying to umpire Damien Dumusois "you're all weirdos".
"I don't care", Tsitsipas replied.
"I feel much better that I could win a match finally in this tournament", Halep said.
'And you're all weirdos.
Tsitsipas admitted the grind of the season has worn on him mentally. The seven months were revealing, of the promise and its pitfalls.
Naomi Osaka's U.S. Open title defence is off to a shaky start.
"I remember achieving my career high of 5 in the world", the 21-year-old said.
"Always at the beginning everything is a bit new, not easy, so I think I played a good match".
'I don't know what this chair umpire has in specific against my team but he's been complaining and telling me that my team talks all of the time when I'm out on the court playing.