Juan Carlos Ferrero's miserable season continued when he was beaten in the US Open second round by Stefan Koubek.
Koubek upset the 2003 runner-up 7-6 (7-2) 4-6 6-7 (6-8) 6-2 6-3.
Ferrero, who has struggled with his fitness for most of the season, had treatment for a leg injury straight after winning the third set.
Koubek seized his chance to level the match and though Ferrero had a 2-0 lead in the decider, Koubek won five games in a row before clinching the win.
"I was fighting a lot and I won the second and third set but then I started to feel a pain in my leg," said Ferrero.
"I couldn't serve and move very well because of my leg."
The 24-year-old admitted he was looking forward to the end of a torrid season, in which he has also suffered early defeats at the French Open and Wimbledon.
"I am not happy with my year. The year is almost finished and I just want to forget it," he said.
"I have some more tournaments to play but this has not been a good year for me."
Ferrero's frustration was evident during the match when he was warned by the umpire for smashing a ball out of the stadium.
He was later penalized a point for abusing an official, prompting the Spaniard to refuse to shake hands with the umpire at the end of the match.