Samantha Stosur dropped an epic second-set tiebreaker but recovered to beat Maria Kirilenko 6-2, 6-7 (15/17), 6-3 on Sunday to reach the quarter-finals of the US Open.
Russia's Kirilenko prevailed in what the WTA said was the longest women's singles tiebreaker at a Grand Slam tournament to knot the fourth-round match at a set apiece.
But it was the ninth seed from Australia who moved on to a quarter-final clash with second-seeded Russian Vera Zvonareva.
Zvonareva advanced with a 6-2, 6-3 victory over Sabine Lisicki, the big-serving German who had hoped to improve on her run to the Wimbledon semi-finals.
Instead Zvonareva, runner-up to Kim Clijsters here last year, needed just 77 minutes to wrap up her fourth career victory over Lisicki in as many meetings.
Stosur has won the last seven of her meetings with Zvonareva, but said she'd take nothing for granted.
"Now we're playing in a Grand Slam," Stosur said. "I'm sure she wants to get one back. Obviously it's a big moment for both of us in the quarters."
Stosur had already entered the record books this week when she toiled for three hours and 16 minutes to get past Nadia Petrova 7-6 (7/5), 6-7 (5/7), 7-5 in the third round - the longest women's singles match recorded at the US Open since the tiebreak era began in 1970.
Last year, Stosur saved four match points to win the latest-finishing women's match in US Open history in her fourth-round defeat of Russian Elena Dementieva.
Stosur said she didn't expect the long hours she'd been putting in to affect her against Zvonareva.
"I actually feel better after this match than what I did the last match," the 2010 French Open finalist said. "Who knows how I'll feel tomorrow morning, but so far, so good."
Stosur, who had dominated in the opening set, said that once the tiebreaker was behind her she "didn't find it too difficult to stay mentally strong.
"I knew if I was going to have a chance to win the match, I had to do that."
Italy's Flavia Pennetta also stayed tough in the face of adversity as she carved out a 6-4, 7-6 (8/6) victory over a fighting Peng Shuai to set up a quarter-final meeting with German Angelique Kerber - a 6-4, 6-3 winner over Monica Niculescu in a battle of unseeded players.
Pennetta, the 26th seed, who shocked third-seeded Maria Sharapova in the third round, had to fight to the finish against Peng, who saved one match point and gave herself four set points in the tiebreaker before Pennetta was able to reach the quarter-finals for the third time in four years.
Pennetta twice came back from service breaks in the second set, but after breaking Peng for a 6-5 lead she was clearly feeling the strain of the long rallies on the steamy Louis Armstrong Stadium.
Serving for the match, she had to pause at the back of the court as she felt herself becoming ill, returning to the baseline to cheers of encouragement of the crowd - and a time warning from the chair umpire.
"I was feeling really bad," Pennetta said. "I think it was because it's really humid. And also, when you are there you have a lot of emotion. My body just needed to breathe, and I started to have the sensation of throwing up. With nothing inside, nothing came out."
When Pennetta failed to convert a match point at 40-30, Peng pounced to seize the game and a quick 5-0 tiebreak lead.
Trailing 2-6 in the decider, Pennetta mustered all of her reserves to win six straight points. She saved the fourth set point against her with a forehand cross-court shot that looked headed for the alley but dropped just inside the line.
That shot, Peng said, was a morale-breaker.
"I also tried to fight," she said, but by that stage, "I couldn't really run."
The quarter-final line-up will be completed on Monday when world number one Caroline Wozniacki faces 2004 champion Svetlana Kuznetsova and three-time champion Serena Williams will tackle another former world number one, Ana Ivanovic.
Seventh-seeded Italian Francesca Schiavone will face Anastasia Pavlyuchenkova and 10th seeded German Andrea Petkovic takes on Spain's Carla Suarez Navarro.