Sixth seed Andre Agassi reached the third round of the US Open when second-round opponent Florian Mayer of Germany retired hurt.
The 34-year-old American had recovered after dropping the second set and was 7-5 2-6 6-2 1-0 ahead when the German quit because of a thigh problem.
"He said he couldn't go on any more," said the two-time former champion.
"It's not the way you like to go through but I thought I was starting to play well and was feeling good."
Agassi, 34, insisted the US Open will not be his last tournament.
"I can definitely say that I will not be retiring after the Open," said the former world number one.
"I think it's very possible that I will play a full schedule, but my priorities have shifted and it's a delicate balancing act."
Third seed Carlos Moya beat American wildcard Amer Delic 6-2 3-6 6-3 6-2 to join Agassi in the third round.
Delic cracked 23 aces during the two-hour contest but Moya's greater experience eventually told as he booked a contest with Belgium's Olivier Rochus.
But Olympic champion Nicolas Massu, seeded 10, crashed out after losing a controversial five-set battle with Armenian Sargis Sargsian.
The Chilean squandered a match point in the fourth-set tiebreak, and his frustration boiled over in the decider.
Having already been warned for racket abuse, Massu was first docked a point for throwing his racket.
Chair umpire Carlos Ramos then awarded the first game of the set to Sargsian, as Massu held up play during a 10-minute argument with the umpire.
He finally bowed out 6-7 6-4 3-6 7-6 6-4 in five hours 10 minutes, the second longest match in US Open history.
Reigning French Open champion Gaston Gaudio bowed out in the second round after a 6-3 2-6 6-4 6-4 defeat to Sweden's Thomas Johansson.
The ninth seed won only one match during the North American hardcourt season and he could not reverse that form against Johansson.
The former Australian Open champion goes on to face Nicolas Kiefer.
Kiefer defeated Greg Rusedski's conqueror Cyril Saulnier 7-6 (7-0) 6-3 7-6 (7-4).
Thailand's Paradorn Srichaphan eased into the third round with a win over Paul Goldstein.
Goldstein, who qualified for the main draw, was playing in his first Grand Slam tournament since 2001.
And though the American fought hard in the first two sets, he eventually succumbed 6-4 7-6 (7-4) 6-0.
France's Fabrice Santoro booked a third-round meeting with top seed Roger Federer with a 6-1 6-3 6-4 win over Russia's Dmitry Tursunov.
And 21st seed Taylor Dent suffered a surprise 6-7 (6-8) 6-4 6-3 7-6 (8-6) defeat to France's Paul-Henri Mathieu.