NEW YORK (AP) ― Mardy Fish found himself dealing with all sorts of problems as he tried to reach the U.S. Open quarterfinals for the second time.

There was the brief flap with his opponent, 11th-seeded Jo-Wilfried Tsonga, and the chair umpire over some distracting cheering in the stands.

There were the aching right hip and hamstring that left Fish flat on his back, getting massaged by a trainer before the fifth set.

There was the pressure of knowing that he was, for the first time, the highest-ranked American at the country’s Grand Slam tennis tournament.

There was the whipping wind that sent shots this way and that.

And then, of course, there was Tsonga, the big-hitting, athletic Frenchman, who feels more confident than ever ― and it shows. The eighth-seeded Fish wasted a lead and lost the fourth-round match at Flushing Meadows 6-4, 6-7 (5), 3-6, 6-4, 6-2 on Monday night, bringing what he saw as a premature end to what he hoped would be a run to a major semifinal.

“This might have been my best chance so far,’’ the 29-year-old Fish said, knowing that he played well all summer on the type of hard courts used at the U.S. Open, including one title, two other appearances in finals and a victory over Rafael Nadal.

“For whatever reason ― old age, I guess ― my body didn’t check up like I had hoped,’’ said Fish, who limped out of his news conference. “Look, that’s not why I lost. But it would have been nice to be able to run without pain.’’

So it will be Tsonga, not Fish, who will take on 16-time Grand Slam champion Roger Federer in the quarterfinals. Federer made it that far for the 30th straight major tournament by beating 36th-ranked Juan Monaco of Argentina 6-1, 6-2, 6-0 in a match that began at 11:50 p.m. Monday night and finished shortly before 1:15 a.m. Tuesday.

Federer played brilliantly right from the start, taking the first five games ― and 20 of the first 25 points ― in only 12 minutes. He didn’t miss a beat in the second set, hitting four aces in his opening service game and finishing with 14.

He earned a rematch against Tsonga, who pulled off a stunner in the Wimbledon quarterfinals two months ago by becoming the first man to beat Federer in a Grand Slam match after dropping the first two sets.

“He’s a tough player. ... I look forward to that match,’’ Federer said. “If I play as good as I did today, sure I have a chance.’’

Talk about an understatement. The statistics looked like a misprint, particularly this one: Federer compiled a 42-4 edge in winners against Monaco.

The start of their match was delayed because the preceding match in Arthur Ashe Stadium ― No. 1 Caroline Wozniacki’s 6-7 (6), 7-5, 6-1 victory over No. 15 Svetlana Kuznetsova ― lasted 3 hours, 2 minutes.
 
“You have to be ready,’’ Federer said.

Wozniacki, seeking her first Grand Slam title, trailed by a set and 4-1 in the second before coming back to beat the 2004 U.S. Open champion.

“I knew that I had to do something,’’ said Wozniacki, who faces No. 10 Andrea Petkovic of Germany next. “I had to do something different.’’

She managed to turn things around thanks to a combination of her own increasingly aggressive play and Kuznetsova’s increased mistakes. Kuznetsova’s 40-20 edge in winners was rendered meaningless by her 78 unforced errors, 52 more than Wozniacki, who reached the U.S. Open quarterfinals for the third year in a row.

Tsonga made it this far in New York for the first time, and unlike Fish, he’s already tasted this sort of success. Tsonga made it to the final of the 2008 Australian Open before losing to Novak Djokovic, and got to the Wimbledon semifinals this year ― where he again lost to Djokovic.

On Monday, Djokovic extended his 2011 record to 61-2 by beating No. 22 Alexandr Dolgopolov of Ukraine 7-6 (14), 6-4, 6-2. Their 16-14 tiebreaker in the first set lasted nearly a half-hour all on its own, with Djokovic saving four set points and finally converting his sixth when Dolgopolov pushed a forehand long to close a 13-stroke exchange.

Both men called that tiebreaker the key to the match. One tiny piece of evidence: Dolgopolov double-faulted twice in the opening game of the second set to get broken, and Djokovic was on his way.

Asked whether he considered winning that energy ― and will-testing tiebreaker to be a physical or mental triumph, Djokovic replied: “Combination of both. But in the end, it was more mental, just to hang in there, try to play right shots at the right time.’’

Djokovic now meets his Serbian Davis Cup teammate and buddy Janko Tipsarevic, who is seeded 20th and made it to the first Grand Slam quarterfinal of his career by beating 2003 French champion and U.S. Open runner-up Juan Carlos Ferrero of Spain 7-5, 5-7, 7-5, 6-2 in a match that lasted more than 3 1/2 hours.

“Strange feeling,’’ Djokovic said. “We are professionals. Certainly we both want to win the match when we play against each other. So you kind of forget about friendship. You put that aside.”