Serena Williams stunned the sports world when she revealed she would be stepping away from tennis following the U.S. Open to focus on her family and her successful ventures off the court.

The 40-year-old will walk away from the sport with 23 Grand Slam titles – the most in the Open Era and second most all-time behind Margaret Court. She will get one more chance to tie the court’s record. She lost in the first round of Wimbledon earlier in the summer.

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Serena Williams in Canada

Serena Williams after her National Bank Open match on Aug. 10, 2022, at Sobeys Stadium in Toronto, Canada. (Julian Avram/Icon Sportswire via Getty Images)

John McEnroe, who partnered with Mixhalo to team up with Will Ferrell to call LAFC’s match against Charlotte FC on Saturday night, told Fox News Digital that Williams was in the upper echelon of all-time great athletes in any sport.

"Serena’s the greatest female athlete, to me, in the history of sports. I don’t care who you could come up with. She’s one of the greatest athletes period – male or female. She’s put herself along the likes of Tom Brady, Michael Jordan, whoever you wanna say … She’s 40 years old. She’s done everything in tennis. She’s got nothing to prove," McEnroe said.

"It sounds like she wants to have more kids, awesome. She’s got a lot of other interests. People want to be a part of what she’s doing. She’ll be doing just fine. We were sort of expecting this to happen. She wanted to win a couple more, one or two more, break the all-time record, win a couple after having her daughter. That doesn’t look like it’s gonna happen but that, to me, doesn’t take away that she’s the greatest of all time."

John McEnroe at Wimbledon 2022

John McEnroe during the Wimbledon Championships, July 3, 2022. (John Walton/PA Images via Getty Images)

SERENA WILLIAMS LOSES FIRST MATCH SINCE ANNOUNCING RETIREMENT

Williams made her announcement in an essay published in Vogue magazine on Tuesday.

Williams admitted in the essay that there was no "happiness" in making the announcement, but she was ready for "what’s next."

"There is no happiness in this topic for me," she wrote. "I know it’s not the usual thing to say, but I feel a great deal of pain. It’s the hardest thing that I could ever imagine. I hate it. I hate that I have to be at this crossroads. I keep saying to myself, I wish it could be easy for me, but it’s not. I’m torn: I don’t want it to be over, but at the same time I’m ready for what’s next."

Serena Williams at the National Bank Open

Serena Williams competes against Belinda Bencic at the National Bank Open in Toronto, Canada, on Aug. 10, 2022. (Zou Zheng/Xinhua via Getty Images)

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The U.S. Open is set for Aug. 29 and will end on Sept. 11.