Top women's seed Karolina Pliskova advanced to the round of 16, coming back from a match point down to beat No. 27-seeded Zhang Shuai of China 3-6, 7-5, 6-4.
Pliskova faced match point at 5-4 in in the second set, but Zhang committed a backhand error and the tall Czech went on to win the game and the second set.
Pliskova, a finalist at Flushing Meadows a year ago, received a trainer massage on her right forearm before returning for the last set. She gutted out that set, coming to the net to swat a cross-court backhand to close out the match.
Pliskova is one of three women still left in the draw - Spaniard Garbine Muguruza and Ukrainian Elina Svitolina are the others - with a chance to end the tournament No. 1. She next faces the winner of the match between American Jennifer Brady and Monica Niculescu.