"She never left my side, she is such a caretaker" - Serena Williams recalls time with physical therapist Esther Lee who is battling cancer

In 2011, Serena Williams overcame a life-threatening pulmonary embolism before making a stunning comeback to tennis. Her physical therapist, Esther Lee, was one of the people who helped her through those tough times.

In an interview with Sports Illustrated, the 23-time Grand Slam singles champion reminisced about her time with Lee, who was recently diagnosed with Stage IV pancreatic cancer. Williams said Lee "never left her side" when she was in the hospital battling for her life over a decade ago.

"She never left my side. And I never asked for that. That meant a lot to me...She is such a caretaker. And beyond anything that I’ve ever seen, beyond anything you could write in a job description," Williams said, looking back at the incident.

Over the years, Lee has worked with many high-profile clients as a physiotherapist. She began working with the dynamic duo of Serena and Venus Williams back in 2009. Serena Williams said she "immediately fell in love" with her in their very first training session.

The former World No. 1 said she found exactly what she needed from Lee's methods of physical therapy. Soon after the first session, Serena Williams asked Lee to join her and Venus Williams full-time.

“Literally asked her on the spot,” Serena said.

“A wonderful, wonderful therapist. So good at what she was doing, and always taking different courses and learning more and more and more, and just wanted to make sure that she was the best she could be," Williams continued.

"And she has a great personality. She’s just really nice—the soul of her being is nice. There’s nothing bad you can say about her," she expressed further.

Williams even went on to call Lee a family member, someone she respects and admires a lot.

“You’re only as good as your team. And she was a big, big, big member of our team. And basically our family, and our lives," the Florida-native said.

In the six years that Lee worked full-time as the American sisters' physical therapist, the younger Williams won 12 Grand Slam titles and an Olympic gold medal in London in 2012. Additionally, Serena and Venus Williams won six Grand Slam doubles titles and doubles Olympic gold in London as well.

Serena Williams' battle with Pulmonary Embolism and blood clots

Serena Williams during the Wimbledon 2018 Championships

Back in March 2011, the then 30-year-old was diagnosed with an illness which could have ended her career. She was on her way to an Oscars party when she experienced difficulty breathing.

At first, Serena Williams felt it wasn't that big an issue, but it was later discovered that she was suffering from several blood clots in her lungs.

By her own admission, things got worse for Williams, who at one point could 'hardly breathe'. Williams battled through pain, recovery and rehab, making it back to the tennis court in a few months. Since recovering from the condition, Serena Williams has won 10 more singles Grand Slam titles and many more big events.

She suffered another ambolism during the birth of her daughter Olympia and was bedridden for weeks as a result.

She hasn't played competitively since her first-round retirement against Aliaksandra Sasnovich at Wimbledon last year, but is expected to return sometime this year.