Italy's Flavia Pennetta carved out a 6-4, 7-6 (8/6) victory over a fighting Peng Shuai on Sunday to reach the quarterfinals of the US Open.
Pennetta, the 26th seed, fired 41 winners with nine aces, but Peng made it a fight to the finish as she saved one match point and gave herself four set points in the tiebreaker before Pennetta was able to finish it off.
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 Louis Armstrong Stadium.
Serving for the match, she was sick at the back of the court, returning to the baseline to cheers of encouragement of the crowd.
After she was unable to convert a match point at 40-30, however, Peng seized the game and a quick 5-0 tiebreak lead over the reeling Italian.
Trailing 2-6 in the decider, Pennetta mustered all of her reserves to win six straight points and reach the quarter-finals of a Grand Slam for the third time.
Pennetta will face Angelique Kerber, whose 36 winners exactly matched her 36 unforced errors in a 6-4, 6-3 victory over Monica Niculescu in a battle of unseeded players.
Kerber, ranked 92 in the world, had never before made it out of the third round of a Grand Slam in 15 prior attempts.
Big-serving German Sabine Lisicki will be out for revenge when she takes on world number two Vera Zvonareva under the floodlights on Arthur Ashe Stadium.
Zvonareva has won all three of their prior encounters, including a straight-sets victory over Lisicki in the second round here last year.
Zvonareva also beat Lisicki at this year's French Open, and at the WTA event in San Diego in August.
"I hope I can get revenge," the 22nd-seed said. "We played here last year and we played in San Diego, those two on hard courts. It was really close in San Diego."
The winner of that match will face either ninth-seeded Australian Samantha Stosur or 25th seed Maria Kirilenko.
Lisicki's sensational run to the Wimbledon semi-finals made her the first German woman to reach the final four of a Grand Slam since Steffi Graf in 1999.
She warmed up for the US Open with a WTA title in Dallas last week and arrived in New York brimming with confidence and ranked in the top 20 for the first time.
She's trying to match -- or even better -- her Wimbledon performance, while Zvonareva is trying to break through for a first major crown after reaching the finals last year at Wimbledon and Flushing Meadows.
The key, she said, would be use all the components of her game.
"I believe I have all kinds of shots and sometimes I'm just not using the whole arsenal," said Zvonareva, who is one of the three of the tournament's four top-seeded women without a Grand Slam title.
That list also includes world number one Caroline Wozniacki, who will face 2004 champion Svetlana Kuznetsova for a place in the quarters on Monday.
With two unproven top seeds, and the early exits of Sharapova, French Open champion Li Na and Wimbledon winner Petra Kvitova, American Serena Williams has stamped herself the women's favourite despite her lowly 28th seeding.
The 13-time Grand Slam champion ousted fourth seed Victoria Azarenka and will battle another former world number one, Ana Ivanovic, for a place in the quarter-finals on Monday.