Nadal battles pain after US Open round 3 win

Defending champion Rafael Nadal sensationally collapsed in agony in the middle of a US Open news conference on Sunday, just two hours after securing his fourth round place.

The 25-year-old world number two was talking to the Spanish media following his third round win over close friend David Nalbandian when he grimaced in pain, screwed up his eyes and slumped in the back of his chair, feeling his right leg. (Also see: Biggest moments of US Open Day 7)

Nadal, a winner of 10 Grand Slam titles, slipped to the floor while tournament medical staff were summoned and scores of reporters and camera crews ushered out of the interview room deep inside the Arthur Ashe Stadium.

After 15 minutes of treatment, Nadal was back on his feet, insisting that the problem was merely cramping.

"It was just cramping in the right leg, in the front and in the back. It was very painful, that's all," said Nadal, who resumed his news conference standing instead of sitting.

A smiling Nadal insisted the incident will not affect his preparations for his fourth round match against Luxembourg's Gilles Muller, scheduled for Tuesday.

"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."

During his 7-6 (7/5), 6-1, 7-5 win over Nalbandian, played out over 2hr 39mins in heavy, 84 degree-heat (29 degrees centigrade) Nadal had also needed treatment on his blistered right foot.

The Spanish star has been plagued by injuries in recent years.

He suffered a serious left foot injury at Wimbledon this year while tendinitis in both his knees saw him suffer a lengthy absence from the tour in 2009.

Muller defeated Russia's Igor Kunitsyn 6-1, 6-4, 6-4, for a place in the quarter-finals.

Muller famously defeated Nadal at Wimbledon in 2005 before the Spaniard got his All England Club revenge this year.

"He's a very aggressive player," said Nadal. "He has a fantastic serve. I have to move him. Probably his movements are the worst thing, but the rest of his game can be really dangerous."

Nalbandian, the Wimbledon runner-up in 2002, saw his challenge on Sunday undermined by 60 unforced errors but he believes Nadal can get even better in the tournament.

"I played a good first set. I had chances but I couldn't take them. Rafa played well, he's a great fighter. I believe he can improve and play even better," said the Argentine.

Spanish fifth seed David Ferrer, a semi-finalist in 2007, defeated German 26th seed Florian Mayer 6-1, 6-2, 7-6 (7/2) and next tackles 2003 winner Andy Roddick.

The American 21st seed, playing in his 12th successive US Open, breezed past French wildcard Julien Benneteau 6-1, 6-4, 7-6 (7/5).