John McEnroe Praises Serena Williams Amid Retirement: 'She's Up With the All-Time Athletes' (Exclusive)

John McEnroe and Serena Williams
LISA O'CONNOR/AFP; Robert Prange/Getty Images

The former tennis star opened up to ET about Williams' legacy, as well as the documentary about his own career, 'McEnroe.'

As Serena Williams is "​evolving away from tennis," retired tennis legend John McEnroe is weighing in on the superstar's indelible legacy.

The outspoken athlete recently chatted with ET's Kevin Frazier, while promoting his forthcoming Showtime documentary McEnroe, and he reflected on Williams' retirement and final US Open.

"I hope it goes well for her, but it doesn’t matter ultimately [because] she's an icon," McEnroe said. "She's like Muhammad Ali, in a way, and Michael Jordan, Billie Jean King, Tom Brady. I mean, she's up with the all-time athletes, whether she wins a match or she wins the tournament."

"I mean, she's won so much, [and] she seems to be in a great place and that’s what matters," he added. "Hopefully she'll be able to sort of inspire more kids to play the sport of tennis in the future."

McEnroe's praise comes nearly five years after the tennis star found himself in hot water over remarks he made about Williams that many critics felt were sexist. McEnroe said in several interviews in 2017 that he felt Williams wouldn't be able to compete against nearly any professional males players. The tennis pro stood by the controversial remarks at the time. He later told CBS This Morning "she's the greatest player, female player, that's ever lived."

Williams penned a first-person account regarding her decision to step back from the sport for Vogue's September 2022 issue, which was published earlier this month. "I’m here to tell you that I’m evolving away from tennis, toward other things that are important to me," she wrote. "A few years ago I quietly started Serena Ventures, a venture capital firm. Soon after that, I started a family. I want to grow that family."

Meanwhile, McEnroe -- who retired in 2006 -- is now taking a look back at his own high-profile and famously tumultuous career in the new Showtime documentary, McEnroe.

"I guess there was enough people that wanted me to look back and they were interested, so that's flattery, I guess," McEnroe, 63, shared.

At the absolute height of his tennis career, in the mid-1980s, McEnroe was famous both for his skill and his outbursts and confrontational behavior on the court. While it would sometimes get in him trouble with umpires, he says it also proved to be a benefit to the psychological aspect of the game.

Addressing his ability to get incredibly heated, but then pull it together and come back for a win, McEnroe reflected, "I'm not quite sure how I did that, but maybe growing up in New York, I was just used to the insanity of it all and the energy of it."

"But, at the same time, I think that’s what infuriated my opponents the most. Not that I lost it, but how quickly I gained it back," he added. "They hated that, cause they thought I was going to melt down."

Fans can learn more about the tennis star's famed legacy when McEnroe airs Sept. 4 on Showtime.