NEW YORK, Sept 2 (Reuters) - Spain's Rafa Nadal lost a set for the first time at this year's U.S. Open on Monday but recovered quickly to safely book his place in the quarter-finals, albeit against an unexpected opponent.
Nadal gave his supporters at Flushing Meadows a brief heart flutter when he lost the opening set to Philipp Kohlschreiber but rebounded to beat the German 6-7(4) 6-4 6-3 6-1.
The 2010 U.S. Open champion, Nadal's next match is against his countryman Tommy Robredo, who pulled off a shock straight-sets win over Roger Federer that ended the prospect of a first U.S. Open showdown between the two greatest players of their generation.
Nadal was in great form in the lead-up to the last major of the year, winning Masters titles in Montreal and Cincinnati, and has continued his red-hot streak at Flushing Meadows.
After struggling with knee problems for years, the world number two has made some slight alterations to his game to help him cope with the demanding hardcourts in North America.
The lefthander has taken some of the speed off his serve to focus more on his accuracy. Against Kohlschreiber, Nadal hit just three aces, but faced only one break point on his serve, which he successfully fought off.
"It was very, very tough conditions," Nadal said courtside.
"Very humid, I sweat too much. The opponent was great and I am lucky to go through.
"Physically it was a very tough match but with my serve, I felt comfortable."
Nadal said Robredo would be in a dangerous mood after beating Federer 7-6(3) 6-3 6-4.