Italy's Flavia Pennetta battled her way to a 6-4 7-6 (8/6) victory over Peng Shuai on Sunday to reach the quarter-finals of the US Open.
Pennetta, the 26th seed, hit 41 winners with nine aces, but 13th seed Peng saved one match point and gave herself four set points in the tiebreaker before Pennetta was able to finish off the match.
Pennetta twice came back from service breaks in the second set, but after breaking Peng for a 6-5 lead she was clearly struggling in the heat on Louis Armstrong Stadium and at one point had to be sick at the back of the court.
Serving for the match, she was unable to convert a match point at 40-30 and Peng was able to claim the game and race into a 5-0 lead in the tiebreak .
But from 2-6 down, Pennetta suddenly found her strength again and won six straight points to reach the quarter-finals at Flushing Meadows for the third time in four years.
The 29-year-old fell in the last eight in 2008 and 2009 but she will fancy her chances of making it through this time against surprise quarter-finalist Angelique Kerber.
The unseeded German's 36 winners matched her 36 unforced errors in a 6-4 6-3 victory over Romanian Monica Niculescu.
Kerber, ranked 92 in the world, had never before made it beyond the third round of a Grand Slam in 15 previous attempts.