NEW YORK (AP) — They broke out odd little dances after hitting big shots, swaying their hips and rocking their arms to music only in their heads.

They pushed their beleaguered bodies this way and that for 4 hours, 44 minutes yesterday, swatting balls from impossible angles and somehow rarely missing the mark.

Through repeated visits from trainers, through all manner of momentum shifts, No. 3-seeded Novak Djokovic and former top-10 player Radek Stepanek produced as entertaining and lengthy a US Open match as there's been in quite some time.

Djokovic has emerged as a potential challenger to No. 1 Roger Federer and No. 2 Rafael Nadal, and on this day, he emerged victorious, if only barely, beating friend and sometime-doubles-partner Stepanek 6-7 (4), 7-6 (5), 5-7, 7-5, 7-6 (2).

When it ended, Stepanek stepped over the net, dropped his racket and trudged over to apply a bearhug so hearty the weary Djokovic nearly toppled over.

"As much as I was running and sliding and cramping, whatever, I still had a lot of fun," Djokovic said. "There are a couple of points that are really unforgettable."

And, oh, how many points there were — 356 in all. The match lasted 63 games, the most at the US Open since 1979. That year, John Lloyd and Paul McNamee played the same number to set the tournament record for most games in a singles match since tiebreakers were introduced in 1970.

"Long day," Djokovic said. "Long match."

It was another super day for his Serbia at another Grand Slam, too, with No. 3 Jelena Jankovic and No. 5 Ana Ivanovic reaching the women's fourth round. Another Serb, Janko Tipsarevic, was scheduled to face Nadal at night.

Also at night, two-time champion Venus Williams was to meet No. 21 Alona Bondarenko, with the winner taking on French Open runner-up Ivanovic.

Williams' younger sister, Serena, got to the fourth round by beating No. 27 Vera Zvonareva 6-4, 7-6 (4). Serena Williams' opponent will be Wimbledon runner-up Marion Bartoli, while No. 1 Justine Henin next plays No. 15 Dinara Safina, who ended the run of Ahsha Rolle of the United States 6-4, 6-3.

Safina's older brother, 25th-seeded Marat Safin, didn't put up much of a fight in a 6-3, 6-3, 6-3 loss to Stanislas Wawrinka. Safin then was reminded that Pete Sampras predicted the Russian would spend many years at No. 1 after winning the 2000 US Open.

"Even the geniuses make mistakes," Safin said.

Wawrinka now meets 2005 semi-finalist Robby Ginepri of the United States. Another American, Mardy Fish, led No. 8 Tommy Robredo 4-1 in the fifth set before dropping the last five games and the match, 6-4, 3-6, 6-4, 6-7 (7), 6-4.

Fish's explanation? "I froze," he said.

That one was played in Arthur Ashe Stadium and lasted three and a half hours, which seemed like nothing in comparison to what went on over at Louis Armstrong Stadium.

"I am totally exhausted. No energy. I smell my shoes — they are so stinky," Djokovic said, then noted that he was fighting cramps "in both of the legs and an arm and back and head".

He got his upper legs massaged a few times. During one break, he plopped down on his stomach so a trainer could knead Djokovic's lower back. Stepanek, too, needed help at changeovers.

Yet both just kept going, remarkably combining for only 88 unforced errors despite the number of shots they hit.

Somehow, both found the strength to play to the crowd, waving their palms or cupping a hand to an ear to ask for louder cheering. Djokovic celebrated a couple of big points by leaping high with a scissor-kick and an uppercut.

Spectators regaled Djokovic and Stepanek with standing ovations during changeovers, before the fifth-set tiebreaker and, of course, at the finish.

"You just want to leave everything you have on the court, you know, to appreciate their support," said Stepanek, a Czech who dropped from a career-high ranking of No. 8 in July 2006 to out of the top 100 after dislocating a disk in his neck. "Novak was the luckier one today, but I can be proud of what I did on the court today."