NEW YORK -- No. 2 Victoria Azarenka rallied from a set down for the second straight match, beating Ana Ivanovic to return to the U.S. Open quarterfinals.

The 2012 runner-up at Flushing Meadows needed 2 hours, 10 minutes to win 4-6, 6-3, 6-4 on Tuesday.

Ivanovic, the 2008 French Open champ, was whipping forehand winners in the first set. Then her serve deserted her, as it has before. The 13th-seeded Serb was broken in nine of her last 11 service games.

But Azarenka wasn't much better, with nine double-faults of her own.

She got into it with the chair umpire for the second straight match, this time over Ivanovic being awarded a winner, instead of the two replaying the point, after a late out call was overturned in the first set.

Unable to serve out the match at 5-3 in the third set, Azarenka finally clinched the victory on her fourth match point. She'll face unseeded Daniela Hantuchova, who played her fourth-round match Monday.

Azarenka's meeting with Ivanovic was pushed back a day by rain, and she looked sluggish after a late-morning start. Azarenka didn't make her first winner until the sixth game.

"I was, like, sleeping," Azarenka said in an on-court interview.

"I really had to wake up in the second set and try to fight for points," she added.

It wasn't pretty: There were five straight breaks to open the second set. After Ivanovic double-faulted on break point for the second straight service game, Azarenka finally held to take a 4-2 lead.

Ivanovic had eight double-faults.

"The second set, I felt I was more determined, more focused," Azarenka said.

The start of the third set was much of the same. Azarenka held in the first game, then there were four straight breaks.

Azarenka had two match points while serving at 5-3 but wasted both with backhand errors.

"The match points were pretty bad," she said. "I really didn't go for my shots. I kept waiting for a mistake, and obviously it didn't happen."

But the way Ivanovic was serving, Azarenka was still in prime position to close out the match, and sure enough, she broke Ivanovic again in the next game to advance.

"This was the big difference, because I felt like I could break her, but it was very frustrating that I was losing my serve constantly," Ivanovic said.