Roger Federer of Switzerland walks off the court after losing in three sets to Tommy Robredo of Spain at the US Open tennis championships in New York September 2, 2013. [Photo/Agencies]

NEW YORK - Former world number one Roger Federer was knocked out of the US Open on Monday by Spain's Tommy Robredo.

In a stunning upset, Robredo won their fourth-round match 7-6(3) 6-3 6-4 at Flushing Meadows.

It was the first time in a decade that Federer, a five-time US Open champion, had failed to make the quarter-finals in New York.

The Swiss master, who holds a record 17 grand slam titles, had his chances against Robredo but converted just two of 16 break points.