New York, Sep 5: Rafael Nadal had a relatively comfortable time on court but a frightening and painful one off it at the US Open, collapsing in agony during his post-match press conference.

The No.2 seed beat Argentine veteran David Nalbandian 7-6 (5), 6-1, 7-5 to progress to the round-of-16 but the toil from the match played in muggy conditions caught up to him in the media room.

He rolled his head back, squeezed his eyes shut, covered his contorted face with his left arm as he stopped taking question.

He paused between deep breaths to plead in Spanish, "Can you call a trainer for me, please?" Then slowly the defending tournament champion slithered out of his chair and onto the ground.

Within minutes, Nadal was sitting up, and then standing, after being given bags of ice to soothe what was diagnosed as leg cramps.

Even if it all amounted to nothing serious medically -- as Nadal and his manager would later insist -- it was a bizarre scene, one at least as memorable as anything that took place on court Sunday at the year's last Grand Slam tournament.

"It's bad luck it happened here," Nadal said, "and not in the locker room."

Andy Murray and David Ferrer -- seeded fourth and fifth respectively -- had much easier Sundays, both notching straight-sets victories.

AP