MASON, Ohio (AP) — Serena Williams plays Tuesday night at the Western & Southern Open in what is expected to be one of her final matches.

It's a big deal, even for a U.S. Open tuneup accustomed to hosting the world's best players.

“Serena Williams is a global icon whose impact certainly transcends tennis,” tournament CEO Katie Haas said. “We are fortunate to have seen her lift our trophy on two occasions and to welcome her here for one of the last events of her incredible career.”

The 40-year-old Williams is preparing to walk away from tennis, saying she wants to have another child and pursue business interests. The 23-time Grand Slam champion has not said what her last event will be, but did make it sound as if her final farewell will come at the U.S. Open, which begins Aug. 29 in New York.

Next up for Williams is Tuesday night's first-round match against 19-year-old Emma Raducanu, the defending U.S. Open champion.

If Williams advances, she could face 2016 Cincinnati champion Karolina Pliskova in the second round. There also is a potential quarterfinal matchup with sister, Venus.

Serena Williams lost 6-2, 6-4 to Belinda Bencic on Wednesday night in Toronto in her first match since she elaborated on her future plans.

“She's been a huge impact on the sport,” said Cincinnati native Caty McNally, who is making her fourth appearance in her hometown tournament. “As a kid I always watched her on the TV. I was lucky to have the opportunity to play her in the U.S. Open a couple of years ago. I think it's important that she's moving on and going to spend time with her family and explore other things in life.”