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 on Louis Armstrong Stadium 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 either qualifier Timea Babos or 15-year-old American wildcard Coco Gauff.

Joining Halep on the exit list was two-time grand slam champion Petra Kvitova.

The no-6 seed was upset by Andrea Petkovic 6-4 6-4.

In some of the other matches, No. 16 seed Johanna Konta beat Margarita Gasparyan 6-1 6-0 while No. 20 Sofia Kenin swept past Laura Siegemund 7-6 (7-4) 6-0.