Today: Men’s matches | Women’s matches

Roger Federer stays up late. (Nick Laham / GETTY IMAGES)

That was some Monday at the U.S. Open.

Caroline Wozniacki struggled a bit before advancing to the quarterfinals, a topic that surely came up in conversation with her new boyfriend.

Caroline Wozniacki, the world’s No. 1 player despite never having won a Grand Slam, rallied from being down a set and a break against Svetlana Kuznetsova and won a 3-hour, 2-minute match, 6-7 (6), 7-5, 6-1.

Wozniacki and the U.S. Open men’s golf champion, Rory McIlroy, are officially an item after flirting on Twitter earlier in the summer. For each to win a U.S. Open this year, McIlroy said, would be “pretty cool.”

“Why it's going so well is that we have so much in common,” McIlroy said, confirming the relationship to “Obviously, different sports, but we're pretty much in the same position at a young age and we can talk about things that probably a lot of 21, 22-year olds can't talk about. It's nice to have someone that sort of understands what you're going through.”

Wozniacki plays No. 10 Andrea Petkovic in the quarterfinals.

The Wozniacki match pushed Roger Federer into an 11:50 p.m. start time — 10 minutes shy of the U.S. Open record for latest start. Federer, while understanding that these things happen in tennis, wasted precious little time in beating Juan Monaco, 6-1, 6-2, 6-0, in a match that ended at 1:04 a.m.

“Nobody trains to go to play at midnight. No player can be ready for that,” Martina Navratilova said on the Tennis Channel. “How do you stay awake? Drink some coffee.”

Tsonga early in the match complained about noise coming from Fish’s friends-and-family box. As the five-set match got away from him, Fish complained about noise from Tsonga’s box, telling the umpire that couldn’t make out what was being said because “I don’t speak French, you dumb---.” Evidently no one called him “Mardy Gras” as a child.

It was all good by the time it ended, though. “I probably shouldn’t have said that,” Fish said (via the Wall Street Journal). “We were fired up.” “With Mardy, it’s all the time friendly,” Tsonga said.

It looks like another long day and late night of tennis lies ahead at the U.S. Open with rain threatening. Weather permitting, three American men — Andy Roddick, John Isner and Donald Young — will be playing for quarterfinal berths.

Young, the wild-card darling of the men’s bracket, plays Andy Murray, the fourth seed from Great Britain; Roddick, seeded 21st, plays David Ferrer of Spain, the fifth seed; and Isner, seeded 28th, plays 12-seeded Gilles Simon of France. Rafael Nadal, last seen sliding to the floor of the interview room with leg cramps Sunday, will play unseeded Gilles Muller of Luxembourg. Nadal is seeded second.