Dominic Thiem's Grand Slam career came to an end in the US Open first round as the former New York champion lost to Ben Shelton on Monday.
Austria's Thiem won his sole major at Flushing Meadows in 2020, coming back from two sets down to beat Alexander Zverev.
However, he struggled badly with a wrist injury afterwards and announced in May that this would be his last year on the tour.
Thiem lost 6-4 6-2 6-2 to Shelton, and the two shared a warm embrace at the net before Shelton gestured to the Arthur Ashe crowd to show some appreciation for his opponent.
There was no crowd present when Thiem lifted the trophy four years ago because of Covid-19 restrictions, but the 30-year-old thanked those who came out to watch this time around.
He was given a framed collage of his best US Open moments in an on-court presentation afterwards.
"It's actually a really important moment for me because I had my greatest success of my career here on this court, in a weird 2020 in very strange and different circumstances," Thiem told the crowd.
"Unfortunately I had this success without any of you, so that was an amazing moment, but on the other hand pretty sad.
"I'm super happy that I got the chance to play my last US Open and I can spend some time with you guys, just to say thank you and to make the time up from what we missed four years ago."
German fourth seed Alexander Zverev and 2022 finalist Casper Ruud were among the winners on the first day's play in New York.
Thiem has 'no regrets'
Thiem, a French Open finalist in 2018 and 2019 and runner-up at the Australian Open in 2020, hopes to retire at his home tournament in Vienna in October.
He was ranked as high as third in the world and claimed important wins over all of the 'Big Three' - Roger Federer, Rafael Nadal and Novak Djokovic.
"I'm here now retiring pretty young, but I'm really happy with the career I had," said Thiem.
"I never expected that it's going to be that successful, so I don't have really any regrets, and I'm good with that.
"I think that the thing I will miss the most is the feeling after winning a great match - it's not really comparable to anything else."
Thiem's rival and friend Zverev overcame a second-set wobble to progress later in New York.
Zverev, still searching for a first Grand Slam title after finishing runner-up to Carlos Alcaraz at the French Open in June, beat compatriot Maximilian Marterer 6-2 6-7 (5-7) 6-3 6-2.
Norway's Ruud beat China's Bu Yunchaokete 7-6 (7-2) 6-2 6-2, while Italy's Matteo Berrettini was a 7-6 (7-2) 6-2 6-3 winner against Spain's Albert Ramos-Vinolas.
Berrettini will face 12th seed and home hope Taylor Fritz, who beat Camilo Ugo Carabelli 7-5 6-1 6-2, next.
Sixth seed Andrey Rublev of Russia also progressed, beating Brazil's Thiago Seyboth Wild 6-3 7-6 (7-5) 7-5.
However, 27th seed Alexander Bublik was the biggest early casualty on the men's side of the draw, losing 6-4 3-6 5-7 6-3 6-4 to China's Shang Juncheng.
Novak Djokovic begins his title defence later on Monday against Radu Albot.
BBC