'Distraught': Tennis world rocked by devastating Serena Williams moment

Serena Williams' first US Open tune-up has ended in dramatic fashion as the American retired with injury while trailing Canadian teenager Bianca Andreescu 3-1 in the Rogers Cup final on Sunday.

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 a back injury.

“She’s distraught,” one TV commentator said as the crowd let out an audible gasp after the umpire announced the match was over.

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Serena then broke down in tears again during her runner-up speech.

"I'm sorry I couldn't do it today. I tried but I just couldn't do it," a tearful Williams, who struggled to get the words out, told the crowd.

"It's been a tough year but we'll keep going."

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.

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

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 during which the former could be heard talking about back spasms.

"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."

Andreescu breaks 50-year curse

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.

In the opening game of the match, Williams survived a break point to hold onto her serve but Andreescu grabbed an early break for a 2-1 lead.

Andreescu then consolidated her break to move 3-1 up at which point Williams immediately moved to her chair where she broke down in tears.

The heartbreaking scenes left the tennis world shattered.