Australian Sam Stosur recovered from losing the longest tie-break in Grand Slam history to beat Maria Kirilenko and reach the US Open quarter-finals.
Stosur prevailed 6-2 6-7 (15-17) 6-3 after seeing five match points slip by in what was the longest ever tie-break in a Grand Slam women's singles match.
The ninth seed had already played in the longest women's singles match at the US Open in the third round.
She will take on second seed Vera Zvonareva in the quarter-finals.
"Obviously I knew it ws pretty long," Stosur said of the tie-break, which stretched the second set to one hour and 24 minutes.
"I lost track of the score, I didn't know at one point if I should be serving or receiving. With all the challenges it was super-exciting. The crowd was into it. I couldn't hear myself think."
Russian Zovnareva beat Wimbledon semi-finalist Sabine Lisicki of Germany 6-2 6-3 in the night match on Arthur Ashe Stadium.
Flavia Pennetta earlier followed up her win over Maria Sharapova with a hard-fought victory over 13th seed Shuai Peng to reach the last eight for the third time.
Italy's Pennetta survived a major wobble at the end of the second set to win 6-4 7-6 (8-6).
Serving for the match at 6-5, she appeared to vomit at the back of the court before being broken.
Pennetta, 29, then fought back from 5-0 and 6-2 down in the tie-break to set up a meeting with Angelique Kerber.
The German defeated Monica Niculescu of Romania 6-4 6-3, but the real drama was in the Louis Armstrong Stadium, where Pennetta had to dig deep to reach the last eight.
Clearly feeling unwell on a humid day in New York, she bent over at the back of the court before recovering her poise.
"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."
After receiving a time warning from the umpire, Pennetta failed to convert a match point with a wayward backhand.
Peng looked certain to force a decider when she earned four set points but couldn't keep her game together, mis-hitting a forehand attempted winner.
Pennetta recovered, winning five points in a row, and sealed victory when Peng missed an easy volley.
The Italian fell in the last eight in 2008 and 2009 but will fancy her chances of reaching the semi-finals when she takes on the unseeded Kerber.