‘I don‘t think I can do this’: Serena Williams breaks down in heartbreaking video

23-time grand slam champion Serena Williams broke down in tears while making a heartbreaking announcement on social media.

American tennis icon Serena Williams broke down in tears while revealing her close friend and physio Esther Lee was battling pancreatic cancer.

In a 92-second clip posted to Twitter, the 23-time grand slam singles champion struggled to contain her emotions while announcing she would be participating in the LA Cancer Challenge 5K to help raise awareness for pancreatic cancer.

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Dr Lee, who has served as the physio for both Williams sisters throughout their stellar careers, is regularly spotted courtside at their matches.

“I don‘t think I can do this, this is going to be too hard,” Williams said, wiping away tears.

“Last year my friend Esther was diagnosed with pancreatic cancer, and she’s been by my side whenever I’ve needed her.

“My dear friend Esther has been a huge part of my own health journey, and now she needs our help as she battles pancreatic cancer.

“Esther has been named the honorary starter for the LA Cancer Challenge 5K walk-run on October 31st in UCLA, benefiting the Hirshberg Foundation for pancreatic cancer research.

“My family and I have joined Team Esther to help support everyone fighting this disease.

“Please join us as we raise awareness and race towards a cure by finding and advancing critical research.”

As reported by Essentially Sports, Williams once admitted she could have died if not for Esther advising her to go to hospital back in 2001.

“I didn’t want to go and she told me, ‘You got to go,’ and that was the beginning of stuff that was really bad but ended up being good for me,” Williams explained at the time.

“I’ve thanked her so many times for that because it literally could have been life changing.”

Sending love to you and Esther. Thank you for raising money for the cause. She may also want to check out PanCan here in LA, which has a terrific patient navigator program.

— lisa baertlein (@LisaBaertlein) October 22, 2021

Esther Lee and Serena Williams. Pictures: Getty Images

Meanwhile, Aussie tennis champion Ash Barty has officially decided to pull out of the remainder of the 2021 WTA season, including the $US14 million ($A19m) WTA Finals.

“I wanted to let everyone know that I won’t be competing in any further tournaments in 2021, including the WTA Finals in Mexico,’’ Barty said in a statement.

“It was a difficult decision but I need to prioritise my body and my recovery from our 2021 season and focus on having the strongest pre-season for the Australian summer.

“With the ongoing challenges of travelling back to Queensland and quarantine requirements, I am not willing to compromise my preparation for January.

“I wish the WTA team and the players all the best for a successful WTA Finals and rest of the year.

“My focus is now on the Australian summer and doing everything I can to win the Australian Open. I can’t wait to play at home again.”