Former top-five player Stefanos Tsitsipas of Greece, who has struggled in recent years, upset 18th-seeded Jiri Lehecka Friday to reach the US Open fourth round for the first time.
Tsitsipas fired four times as many aces as his Czech opponent, closing the match with a service winner to defeat the Czech 2-6, 6-1, 7-6 (7/3), 6-1.
Tsitsipas saluted the crowd, saying "you carried me through this match" after an on-court interviewer referenced vocal support from New York's sizeable Greek-American population.
The win follows Tsitsipas' first-round upset of rising star Arthur Fils and places the Greek in the round of 16, his furthest appearance in a Grand Slam in more than two years.
After the two men split the first two sets, the third-set tiebreaker proved decisive, with Tsitsipas serving two aces in a row, while Lehecka, a quarterfinalist in New York last year, double faulted and misfired ground strokes.
Tsitsipas had 34 winners in all to Lehecka's 22, while committing 30 unforced errors compared with 41 for the Czech player, a quarterfinalist in New York last year.
Tsitsipas said he was pain-free after back problems derailed his 2025 campaign.
"This season might not have been the best that I've had, but at least I wake up every single day, I'm happy that I don't have any pain, and I know I can go practice without any uncertainty of how my body is going to respond," he said.
A former two-time Grand Slam finalist, Tsitsipas, 28, was a mainstay of the top 10 in the first part of the 2020s after bursting on the scene as an heir apparent to tennis greats Roger Federer, Rafael Nadal and Novak Djokovic.
But he has been among the players eclipsed by the rise of Spain's Carlos Alcaraz and Italy's Jannik Sinner. Besides injuries, Tsitsipas has also grappled with a complicated relationship with his father, Apostolos Tsitsipas, who has also worked as his coach.
In June, Tsitsipas parted ways with Apostolos as coach, describing the move as permanent. He is now working with Thomas Perrin and Patrick Mouratoglou.
"I don't know if it is at the right time, but it is happening," Tsitsipas said. "In Greece, we have a saying, 'It's better late than never,' so I go by that."
