MONTREAL -- Former world No. 1 Serena Williams has withdrawn from the Rogers Cup.

Germany's Tatjana Maria will bypass the qualifying tournament that began Saturday morning, taking Williams's spot in the main draw. Maria will face France's Alize Cornet in the first round.

"Of course, we are disappointed that Serena will not be joining us. Fans were very much looking forward to seeing her in action," said Eugene Lapierre, tournament director of the women's side of the Rogers Cup. "But beyond the disappointment, the tournament, as a whole, remains a high-level competition. The entire Top 10 is here, along with 22 of the Top 25. There are exciting matches in store from the outset."

Williams was No. 1 on the WTA world rankings after beating her sister Venus to win the 2017 Australian Open. Shortly after the win, she announced that she was pregnant and didn't play for the rest of the tennis season.

Since returning to action at this year's French Open, Williams has risen to 26th in the WTA rankings.

The 36-year-old Williams was the runner-up at Wimbledon last month. That was just her fourth tournament since returning to the tour after having a baby in September and dealing with a health scare related to blood clots.

The 23-time Grand Slam champion is coming off the most lopsided defeat of her career, a 6-1, 6-0 loss to Johanna Konta in San Jose, California, on Tuesday.

The year's last major tournament, the U.S. Open, starts on Aug. 27.