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World number two and defending champion Rafael Nadal fought his way into the fourth round by beating Argentina's David Nalbandian in the US Open at Flushing Meadows.

The Spaniard was given a hard time in the first set, which itself lasted 62 minutes, but asserted his authority in the second and third. Nalbandian was beaten 7-6 (7-5) 6-1 7-5 but is due his fair share of credit for giving the 24-year-old Spaniard a torrid time in the first set.

It was the opening match at the Arthur Ashe Stadium and Nalbandian managed to break Nadal in his third service game. He looked on course to take the first set, but lost his nerve at the crucial juncture. The Argentine double-faulted while at break-point allowing Nadal to seize the lifeline and comeback.

It went down to a tie-break, wherein Nadal took the lead after another Nalbandian double-fault at 3-3. Unlike his opponent, the Spaniard held his nerve at the crucial point to take the set.

In the second, Nadal bombarded the Argentine with power-strokes. He broke thrice on his way to a two-set lead. Nalbandian seemed to make his own comeback when he broke Nadal in the opening game of the third, but Nadal recovered to break-back and serve for match. He was surprisingly broken again, but Nalbandian proved to be his own worst enemy. Needing to hold serve to take the set into tie-breaker, he double-faulted again, handing the match to Nadal.

It was a tough day, said Nadal afterwards. David is a fantastic player and a close friend who has had a tough time with injuries.

The first set was key when I came back when he was serving for the set. I am happy because I played my best match of the tournament so far.

Worryingly though, during his post-match press conference, Nadal winced in pain and slid from his chair to the floor clutching his right leg. He needed treatment for 15 minutes. Fortunately, he made a full recovery and resumed the press conference.

It was just cramping in the right leg, in the front and in the back. It was very painful, that's all, said Nadal. I will train normally on Monday. It was just a normal cramp that could have happened anywhere, but it happened in the press room. Anywhere else, nobody would have noticed.

The Spaniard will take on Gilles Muller of Luxembourg in the last-16 phase of the tournament, after he beat Russia's Igor Kunitsyn 6-1 6-4 6-4.

In the later match at the Arthur Ashe Stadium, British number one Andy Murray secured his place in the fourth round with an uneventful victory against Spain's Feliciano Lopez.

The Scot continued his formidable head-to-head record against the Spaniard with a sixth consecutive win. He dominated proceedings through the game to secure a 6-1 6-4 6-2 victory.

He will now play Donald Young in the fourth round on Tuesday.

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