Roger Federer returns a shot to Jo-Wilfried Tsonga in the quarterfinals at the U.S. Open in New York, Thursday. Federer won the match.

NEW YORK — At one point, Andy Roddick looked up and saw a fan scaling a chain-link fence behind tiny Court 13, hoping to catch a peek of the 2003 U.S. Open champion’s victory Thursday.

At another point, a baby’s loud cries provided a distraction at the 584-seat venue.

“At least,” Roddick deadpanned later, “there wasn’t a baby crying on the fence.”

It was that sort of day at this most unusual U.S. Open.

Rain finally gave way to sun in the morning, but chaos still managed to reign. A crack near a baseline in the tournament’s second-biggest stadium let water seep through, halting Roddick’s already twice-delayed match against David Ferrer until they were moved to a court often used by juniors.

And because of showers earlier this week, the U.S. Tennis Association extended the tournament, delaying the men’s final by 24 hours to Monday at 1 p.m. PDT. The women’s final was shifted from Saturday night to Sunday at 1 p.m. PDT.

Amid all of Thursday’s goings-on — which also included complaints about the schedule both before and after it was changed; talk by Roddick and others about forming a union; and treatment by a trainer for both No. 1 Novak Djokovic and his opponent, who eventually quit, then apologized to Djokovic — at least there was plenty of tennis played, quite a change from Tuesday’s total washout and Wednesday’s 15 minutes of action.

Roddick, defending champion Rafael Nadal, Andy Murray and John Isner all won to reach the quarterfinals. On the other side of the men’s draw, Djokovic and Roger Federer set up a semifinal showdown; it’s the fifth consecutive year they’ll meet at the U.S. Open and a rematch from this year’s French Open, where Federer handed Djokovic one of his two losses in 2011. Serena Williams, Caroline Wozniacki, Sam Stosur and Angelique Kerber filled the four spots in the women’s semifinals.

Given the delays, the 21st-seeded Roddick was eager to get going against the fifth-seeded Ferrer somewhere — anywhere, really.

They got in less than 10 minutes Thursday before Roddick pointed out a damp spot in Louis Armstrong Stadium that made it too dangerous to play. He and Ferrer headed back to the locker room while workers spent an hour trying to dry the area. At 12:30 p.m., the players returned with tournament referee Brian Earley to inspect the area.

Roddick pointed out that the spot still was wet and said to Earley, “Can you tell us why you brought us out here? … How hard is it to not see water? … What are we doing here?”

As he walked to the sideline, Roddick shook his head and said: “I’m baffled right now. Absolutely baffled.” He shoved his racket in his bag and walked off the court, as some fans jeered.

Roddick, Ferrer and Earley then spoke in a hallway of 10,103-seat Armstrong stadium.

“Put us on 13. Thirteen’s open. Let’s go play. I don’t care where we play,” Roddick said.

Within minutes, the decision was made to switch courts, sending fans running and pushing their ways over to the metal bleachers at Court 13, and the match eventually resumed a little before 1 p.m. local time.

Not much more than two hours later, Roddick was high-fiving front-row spectators after wrapping up his 6-3, 6-4, 3-6, 6-3 victory.

Elsewhere, No. 2-seeded Nadal beat 68th-ranked Gilles Muller, of Luxembourg, 7-6 (1), 6-1, 6-2 in Ashe; No. 4 Murray eliminated 84th-ranked Donald Young, of the United States, 6-2, 6-3, 6-3 in the Grandstand; and No. 28 Isner got past No. 12 Gilles Simon, of France, 7-6 (2), 3-6, 7-6 (2), 7-6 (4) on Court 17.

Murray plays Isner, who reached the first Grand Slam quarterfinal of his career.

In the night’s last match — which was interrupted by rain for 1 1/2 hours in the first set — Federer beat No. 11 Jo-Wilfried Tsonga 6-4, 6-3, 6-3 to reach the U.S. Open semifinals for the eighth year in a row. Five of Federer’s 16 Grand Slam titles came in New York.

Djokovic reached his sixth consecutive major semifinal and improved to 62-2 this season, advancing when his opponent, No. 20 Janko Tipsarevic, stopped playing while trailing 7-6 (2), 6-7 (3), 6-0, 3-0. Tipsarevic had his left hamstring bandaged by a trainer at 5-0 in the third set.

Djokovic needed his own visit from the trainer for treatment on a bloody left big toe after sliding to get to a drop shot in the fourth set’s opening game.

In the women’s quarterfinals, 13-time major champion Williams overcame some shaky serving early to beat No. 17 Anastasia Pavlyuchenkova, of Russia, 7-5, 6-1 and improve to 17-0 on hard courts this season.

“I just kept losing serve in the beginning. Very weird,” said Williams, whose older sister Venus watched from the stands.

Seeded only 28th after missing nearly a full year because of health problems, Williams hasn’t dropped a set so far heading into a semifinal against the top-seeded Wozniacki, a 6-1, 7-6 (5) winner against No. 10 Andrea Petkovic, of Germany, on Court 13.

On the other half of the women’s draw, No. 9 Sam Stosur will play 92nd-ranked Angelique Kerber, of Germany, in the semifinals. Kerber upset No. 26 Flavia Pennetta 6-4, 4-6, 6-3, while Stosur easily defeated No. 2 Vera Zvonareva 6-3, 6-3. Zvonareva was the runner-up at the U.S. Open and Wimbledon last year.