Coco Gauff is out of the US Open on Day 1.

Anastasija Sevastova knocked off the 16-year-old Gauff in three sets, 6-3, 5-7, 6-4, on Monday.

It was Gauff's earliest exit from a Grand Slam tournament in four appearances. A year ago, Gauff made it to the third round at Flushing Meadows before losing to 2018 champion Naomi Osaka in a match that ended in tears for the teen and a hug from the winner.

Sevastova had been just 1-8 in singles in 2020 and got the breakthrough win she needed again in New York. Sevastova was a semifinalist at the US Open two years ago.

Gauff had 13 double-faults.

Earlier Monday, top-seeded Karolina Pliskova advanced in straight sets.

Pliskova surged ahead of Anhelina Kalinina 4-1 in the opening set, lost three games in a row, then took the last eight for a 6-4, 6-0 victory. Pliskova had a 26-7 edge in winners.

She is ranked third in the world but has the top seed in New York.

With staff and spectators limited due to the coronavirus pandemic, cavernous Arthur Ashe Stadium was eerily quiet for Pliskova's match.

"I was like, 'Should I cheer myself?'" Pliskova said.

In other early action Monday, three-time Grand Slam champion Angelique Kerber eliminated Ajla Tomljanovic 6-4, 6-4.

Kerber won the 2016 US Open but lost in the first round last year. She used to be ranked No. 1 and is seeded 17th in New York.

There were only about 15 people in the seats of Louis Armstrong Stadium for the start of Kerber's match.

"It's kind of a little bit the feeling when you play, like, practice matches," Kerber said.

Kristina Mladenovic, who is among a reported seven players under advanced coronavirus protocols, beat Hailey Baptiste 7-5, 6-2. Mladenovic had contact with Benoit Paire, who a source identified to The Associated Press on Sunday as the player who tested positive for the coronavirus and was removed from the tournament field.

"I am basically in a new 'bubble in the bubble,' so there's not very much I'm allowed to do, which makes it tough for me to compete and mentally be kind of fresh and ready," said Mladenovic, seeded 30th.

The 2019 French Open runner-up, Marketa Vondrousova, also advanced, beating Greet Minnen 6-1, 6-4.

The Associated Press contributed to this report.