Former world No. 1 Naomi Osaka lost in the first round of the French Open on Monday, 12 months after controversially quitting the tournament.

Osaka, a four-time Grand Slam champion, was knocked out 7-5, 6-4 by American 27th seed Amanda Anisimova – the same player who ended the Japanese star's title defense at the Australian Open this year.

An error-plagued Osaka served up eight double faults and committed 29 unforced errors on her return to Roland Garros, after withdrawing in 2021 when she refused to honor mandatory media commitments before revealing she had been suffering from depression.

"It's tough to see Naomi Osaka in the first round so I knew it wouldn't be easy," said Anisimova, who reached the semifinals in Paris three years ago.

"I knew I had to play my best tennis and the conditions were not easy."

Women's title favorite Iga Swiatek, in the meanwhile, stretched her winning streak to 29 matches.

As rain fell on the outside courts, Swiatek required just 54 minutes to dispatch Ukrainian qualifier Lesia Tsurenko 6-2, 6-0 under the roof on Court Philippe Chatrier.

The 20-year-old Swiatek, who took over as world number one following Ashleigh Barty's shock retirement, has won her last five tournaments and is bidding for a second French Open in three attempts.

"Today was a pretty good match," said Swiatek.

"I love playing here even though the last couple of days it's been raining and pretty dark."

The 2020 champion will play Ukraine's Dayana Yastremska or American Alison Riske for a spot in the last 32.

Swiatek is unbeaten since February and has the longest winning streak on the WTA tour since Serena Williams won 34 matches in a row in 2013.

"I'm pretty sure that it can end, but I just want to keep going. I'm sure someday my streak will stop.

"I'm just focusing on tennis and playing my game, not on stats or some numbers."