Roger Federer's failed to halt his slump as he suffered a straight-sets defeat against Tommy Robredo in the fourth round of the US Open.
The 17-time grand slam champion, who was recently dumped out in the second round of Wimbledon before losing to the likes of Daniel Brands and Federico Delbonis on the ATP Tour, was beaten 7-6 (7-3) 6-3 6-4 by the 19th-seeded Spaniard.
Federer never looked comfortable after a long rain delay prompted organisers to move the match from Arthur Ashe Stadium to Louis Armstrong, a court Federer had not played a match on for seven years.
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Robredo, who had never beaten Federer in 10 previous meetings, was a break ahead twice in the opening set and, although Federer pushed him to a tie-break, it was dominated by the Spaniard.
The Swiss was making odd tactical decisions, rushing to the net at the wrong moments and making too many unforced errors as he went two sets down.
The crowd tried to inspire Federer to a fightback in the third set but it was Robredo who gained the crucial advantage with a break for 4-3, and clinched the biggest win of his career shortly afterwards.
"I kind of feel like I beat myself, without taking any credit away from Tommy," a dejected Federer said.
"Clearly he was making sure he was making many balls. It was up to me to make the difference and I couldn't.
"I kind of self-destructed, which is very disappointing, especially on a quicker court. Your serve helps you out. You're going to make the difference somewhere.
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"I just couldn't do it. It was a frustrating performance."
The statistics backed up Federer's claims as five-time champion at Flushing Meadows made 43 errors in three sets, while he converted just two break points from 16 chances.
However Federer, now 32, insists that he can bounce back from the loss.
"It just ended up being a bad combination of many things," he said.
"So I've definitely got to go back to work and come back stronger, get rid of this loss now as quick as I can, forget about it, because that's not how I want to play from here on.
"I want to play better. I know I can. I showed it the last few weeks, that there is that level. So today was pretty frustrating."
Robredo's reward is a quarter-final showdown with compatriot Rafael Nadal, who recovered from a slow start to beat Philipp Kohlschreiber 6-7 (7-4) 6-4 6-3 6-1.