NEW YORK (AP) — Caroline Wozniacki knew her lengthy match at Flushing Meadows was delaying bedtime for a certain fan of hers: boyfriend Rory McIlroy, the U.S. Open men’s golf champion.

Tennis players can’t use cell phones or computers when they’re on court, so the top-seeded Wozniacki had no way of knowing that McIlroy tweeted, “COME ON!!!!!!” at 10:49 p.m. EDT Monday night. There still were 40 minutes to be played in Wozniacki’s 6-7, (6), 7-5, 6-1 comeback victory over Svetlana Kuznetsova, which put the 21-year-old from Denmark into the U.S. Open quarterfinals for the third year in a row.

“I know Rory was watching, so I think I kept him up for quite some time. I feel a bit guilty,” Wozniacki said with a smile after the 3-hour, 2-minute match. “Now he can sleep well, because I won.”

Wozniacki trailed by a set and 4-1 in the second, a daunting deficit for anyone.

“I was basically out of the tournament at one point,” she said.

But she took four consecutive games there to start turning things around, and wound up winning 12 of the match’s last 14 games to extend her bid to win her first Grand Slam title.

That lack of a major trophy is a constant topic of conversation about Wozniacki.

“She’s still great player,” said Kuznetsova, the champion at the 2004 U.S. Open and 2009 French Open. “What’s wrong if she didn’t win a Grand Slam?”

Wozniacki’s best showing at a major tournament came at the 2009 U.S. Open, when she reached the final. She erased a sizable deficit in the fourth round that year, too, against — you guessed it — Kuznetsova.

Wozniacki said she thought back to that earlier comeback, telling herself: “OK, I can do this. I can still fight back.”

And she did just that, mostly in her typical fashion: chasing down ball after ball, making fewer mistakes than her opponent, and winning plenty of long points.

She finished with 26 unforced errors, 52 fewer than Kuznetsova.

“She was a wall,” Kuznetsova said. “To break a wall, you cannot hit hard. You have to mix it up.”

After all of her early problems, including blowing a 5-2 lead in the first-set tiebreaker, Wozniacki eventually made one significant strategic change.

She began to play more aggressively in the latter stages of the match.

“I just stepped into the lines a little bit and went for my shots a little bit more,” Wozniacki said.

She’ll play 10th-seeded Andrea Petkovic in the quarterfinals Wednesday, and said there are no concerns about having spent so much time on court Monday. Wozniacki’s match didn’t end until 11:29 p.m., and she didn’t hold her news conference until an hour later.

“I know that I’m in good shape,” Wozniacki said. “I can play out there for five hours if I have to.”

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