UPDATE 1-Tennis-Djokovic caps perfect day for centre court seeds

* Wins tiebreaker 8-6 to close out match

* Entertaining tilt ends seeds' perfect center court day

(Adds detail, quotes)

By Larry Fine

NEW YORK, Sept 2 (Reuters) - Novak Djokovic capped a perfect Thursday for the favourites at the U.S. Open with an entertaining victory over Germany's Philipp Petzschner to reach the third round of the year's final grand slam.

Third-seeded Djokovic closed out an irresistible display by the seeds with a lively 7-5 6-3 7-6 win under the lights at Arthur Ashe Stadium.

The Serb's victory marked the fifth successive straight-sets win for seeded players on centre court, although he was forced to work harder than his predecessors against a spirited opponent armed with a formidable serve.

The keenly contested encounter was 12 games old before Djokovic managed the first service break, taking a lot of energy out of both players and leading to an unusual third set tiebreak where seven points in a row were won against serve.

Djokovic squandered two match points, double-faulting on the first when serving at 6-4 and then hitting a forehand into the net on the second.

The 52nd-ranked Petzschner, who teamed with Austrian Jurgen Melzer to win this year's Wimbledon doubles title, sailed a second serve return long to end the two-hour 23-minute match.

"He's a very good player, you have to give him credit," Djokovic said. "He serves well. He was changing up the pace and not giving me any rhythm. I was just fortunate to hold on.

"It was very shaky at the end of the match but I was just fortunate to hold on."

The crackling match saw a brief interruption when a fight broke out in the upper deck in which three people were handcuffed and taken away in a dispute over "bad language" according to officials.

Petzschner also seemed a little rattled at times and slugged two balls into the crowd out of frustration.

Djokovic saved the best bit of entertainment for the last in post-match comments on the court.

Exhorted by fans late in the contest to match Swiss master Roger Federer's famed back-to-the-net, between-the-legs winners as the Serb raced back for a ball against Petzschner, Djokovic instead ripped a backhand winner.

Asked by the interviewer if he had that "tweener shot between your legs," Djokovic offered a perfectly timed comedy reply.

"No. I have something else between my legs," he quipped, eliciting roars of laughter and applause from the centre court fans.

"But don't worry, I will not show it to you tonight."

Djokovic, U.S. Open runner-up to Federer in 2007 and beaten semi-finalist by the Swiss in the last two tournaments, will next face unseeded American James Blake, who advanced against Canadian Peter Polansky. (Reporting by Larry Fine, Editing by John O'Brien; To query or comment on this story email sportsfeedback@thomsonreuters.com)