The top women's seed in the US Open, Naomi Osaka, was defeated by 13th seed Belinda Bencic on Monday in the Round of 16. Osaka went down 5-4, 7-6 against the Switzerland native. 

In front of a crowd at Arthur Ashe Stadium in Queens, Bencic, 22, took down the top-seeded women's tennis player in the tournament. She had high praise for her opponent and said she was pleased with her own performance.

"She's a great player and I had to be at the top of my game. I'm really pleased with how I played and managed my nerves," Bencic said of Osaka.

Osaka, who beat Serena Williams last year in a controversial ending to the US Open, was coming off a win against young star Coco Gauff, who she beat 6-3, 6-0 on Saturday. The defending champion has been dealing with a left knee injury and was visibly favoring one leg. 

Bencic has already defeated Osaka in three of their four official matches this year. With this last win over Osaka, she will face Donna Vekic, who defeated Julia Goerges on Monday. 

This is the second No. 1 in the tournament to go down in the past two days, as Novak Djokovic had to retire from his match on Sunday due to a shoulder injury.