Naomi Osaka continued her bid for a second straight US Open title with a business-like 6-3 6-4 win over Magda Linette, but No.4 seed Simona Halep is out.
Wimbledon champion Halep's disappointing record at Flushing Meadows continued with a defeat by Taylor Townsend in the second round.
The American qualifier won 2-6 6-3 7-6 to end Halep's tournament, where the Romanian made it past the opening round for the first time in three years.
Halep managed to fight off a pair of match points in the 10th game of the decider but Townsend's aggressive play at the net carried her home.
Townsend, 23, used an aggressive, net-rushing style of play to keep the pressure on Halep, who grew more and more frustrated as she was unable to come up with the necessary passing shots.
"This means a lot. It has been a long journey," said Townsend. "This match means so much and gives me so much confidence that I can do it.
"Before I played not to lose, today I played to win. I told myself this is an opportunity. You have nothing to lose; go for it."
Osaka, after struggling with nerves in her gruelling first-round match, was calm and collected as she smacked 13 winners to dispatch Poland's Linette.
After a one-sided first set, trouble brewed for the world No.1 when Linette raced out to a 3-0 lead in the second on a sun-soaked court.
But the 21-year-old Japanese kept her composure and battled back, hitting a deft volley on match point to seal the win before an adoring crowd that included former San Francisco 49er Colin Kaepernick and former Los Angeles Laker Kobe Bryant.
Next up for Osaka is 15-year-old American wildcard Coco Gauff.
The teenage sensation brought loud cheers from Louis Armstrong Stadium with a 6-2 4-6 6-4 win over Timea Babos in two hours and 23 minutes.
"It's been amazing. She played so good, I am just happy to win. I was tested a lot. Anyone could have won," said Gauff, who first gained fame with last month's Wimbledon run where she reached the fourth round from qualifying.
Joining Halep on the exit list was two-time grand slam champion Petra Kvitova and No 9 seed Aryna Sabalenka.
The no-6 seed was upset by Andrea Petkovic 6-4 6-4 while Sabalenka was beaten by Yulia Putintseva 6-3 7-6.
Former Australian Open champion Caroline Wozniacki rallied back to beat American Danielle Collins 4-6 6-3 6-4.
The Danish 19th seed, who has not been past the second round in New York since her run to the semi-finals in 2016, secured the victory when she served out to love in the final game.
In some of the other matches, No. 16 seed Johanna Konta beat Margarita Gasparyan 6-1 6-0, Sofia Kenin swept past Laura Siegemund 7-6 (7-4) 6-0, Julia Gorges defeated Francesca Di Lorenzo 7-5 6-0, No.7 Kiki Bertens overcame Anastasia Pavlyuchenkova 7-5 6-4, Belinda Bencic eliminated Alize Cornet 6-4 1-6 6-2, Bianca Andreescu was too strong for Kirsten Flipkens, winning 6-3 7-5, and Donna Vekic accounted for Kaia Kanepi 7-5 6-3.
AAP.
