Serena Williams loses first match since announcing she is nearing retirement.

TORONTO — Serena Williams lost her first match since telling the world she is ready to leave professional tennis.

No one knows exactly how many more matches Williams will play before walking away, and the 23time Grand Slam champion exited the National Bank Open on Wednesday night with a 6-2, 6-4 loss to Belinda Bencic.

“A lot of emotions, obviously,” Williams said, her voice shaking during an oncourt interview.

“I wish I could have played better,” she told the fans. “Belinda played so well today.”

The second-round match at the hard-court tuneup for the U.S. Open came a day after the 40-year-old Williams announced “the countdown has begun” on her playing career, saying she wants to have another child and pursue business interests.

She did not state precisely what her last event will be, but did make it sound as if her final farewell could come at the U.S. Open, which begins Aug. 29 in New York.

“It’s been a pretty interesting 24 hours,” Williams said after Wednesday’s match.

“I’m terrible at goodbyes,” she said, her hand on her chest, “but goodbye, Toronto!”

Williams, a three-time champion in the Canadian city, started the match, fittingly enough, with an ace. Delivered another later in that opening game, too, showing off the superb serve that helped her to so many victories.

But because of a leg injury that sidelined her for the last half of 2021 and first half of 2022, she was playing for only the third time in the past 12 months, and it showed.

It did not help Williams that she was facing an opponent 15 years her junior and quite talented, to boot: Bencic is ranked 12th, won a gold medal for Switzerland at the Tokyo Olympics last year and has been a Grand Slam semifinalist.