Serena Williams heading to Cincinnati 'to see what happens' after back spasms force withdrawal in Toronto

The 23-time major winner hopeful she can compete despite having to tearfully forfeit in Toronto

Serena Williams withdrew after just four games of the Rogers Cup final in Toronto. Getty

Serena Williams still plans to try and compete in Cincinnati despite having to withdraw from Sunday's Rogers Cup final due to back spasms.

The American was forced to retire while trailing Canadian teenager Bianca Andreescu 3-1 in Toronto on Sunday.

Williams is scheduled to compete in Cincinnati this week, starting with a first-round match with a qualifier on Tuesday.

"As of now, I'm going to go to see what happens," Williams said of her plans for this week.

Williams, who hopes to chase a record-equalling 24th career grand slam title at the US Open, seemed fine on court but suddenly sat crying in her chair before deciding to retire 19 minutes into the match with back spasms.

"I'm sorry I couldn't do it today. I tried but I just couldn't do it," an emotional Williams, who struggled to get the words out, told the crowd. "It's been a tough year but we'll keep going."

Andreescu consolidated an early break on Sunday to move 3-1 up at which point Williams went to her chair where she called for the trainer and broke down in tears.

Williams said the spasms began during her three-set semi-final win over Czech Marie Bouzkova on Saturday. They got so bad that she was unable to sleep and could not really move but she added that she at least wanted to try and play the final.

"I was just trying to figure out how do you play a match where you have no rotation?" said Williams.

"And I don't want to get this far and not at least try. I think I would have really regretted not at least going out there and seeing maybe if a miracle happened."

The 37-year-old Williams, whose competitive action this year has been severely limited because of knee issues, declared herself pain-free ahead of the tournament, which she was hoping to use as a springboard for the rest of her hardcourt swing.

But the six-times US Open champion, still without a title since returning from maternity leave in 2018, now faces her latest injury setback with the year's final grand slam just two weeks away.

Williams, who is due to compete in Cincinnati next week, said she has experienced back spasms a lot in her career and that if this latest episode plays out like those before, she does not expect it to keep her out of any events.

"They're incredibly painful, but it goes away after, like, 24, 36, maybe 48 hours, and like clockwork," said Williams.

"In that first phase, it is incredibly painful, to a point where I usually don't get out of bed. So if it's what typically happens, I will be fine, but I have to wait and see."

As Williams sat dejected in her chair, Andreescu, who is no stranger to injury setbacks, went over to console her. The pair embraced and had a heartfelt conversation.

Andreescu, who shot to prominence with her Indian Wells triumph in March and was competing this week for the first time since withdrawing from the French Open with a shoulder injury, is the first Canadian to win the event in 50 years.

"I feel for Serena so much. I've been through so much the last year with injury so I am so sorry she had to go out this way," the 19-year-old said during the trophy ceremony.

"Sometimes, you can't push your body and she couldn't today and I wish her a fast recovery."