Serena Williams and her former coach, Patrick Mouratoglou, made some magic on the tennis court together, but their relationship was not always a walk in the park. 

In an interview with The Guardian, Mouratoglou, 55, recalled a fight he had with Williams, 43, after she gave birth to her first daughter, Olympia, in September 2017. 

“It was after the pregnancy – not right after; I know these things take time,” Mouratoglou said in the story, published on Thursday, September 11. “I told her, ‘Listen, this is not a comment on how you look. It’s not my problem. But tennis is a sport in which you can’t afford to be overweight.’”

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He added, “In Serena’s case, she was older – so of course the body is not going to bounce back the same as before, and the risk of injury is even bigger. We had a few fights about it. I remember she did not like when I said that because she thought I was judging her.”

Mouratoglou coached Williams from 2012 to 2022, a stretch in which the tennis star won 10 of her 23 Grand Slam singles titles. 

“I kept telling her, ‘I don’t care about your look. It’s not my job. My job is your tennis,’” Mouratoglou recalled saying to Williams. ‘“If you want to come back to the top and make history, then we have to be very efficient on every level – including this one.’ Which for me was the key element.”

Mouratoglou explained how even the slightest amount of weight gain can be detrimental to a tennis player’s performance. 

“It’s a sport in which you change directions all the time and with a lot of speed,” he said. “Even one [pound] overweight is a lot. When you go full speed in one direction with one [pound] extra and then need to stop and come back, the time that you lose is really important.”

Last month, Williams revealed she had lost 31 pounds after going on the GLP-1 medication Ro.

When Mouratoglou was asked if he wished Williams had “done this five, six years ago,” his answer was blunt. 

“I’m not the type of guy who’s looking back and having regrets,” he said. “But, yeah, if she would have been in this position physically, the results would have been better.”

Williams retired from professional tennis in 2022. She and her husband, Alexis Ohanian, welcomed their second daughter, Adira, in August 2023. 

In announcing her use of the weight-loss medication, Williams said she was “never” able to reach the weight she “needed” after giving birth to Olympia.

“It was crazy because I’d never been in a place like that in my life where I worked so hard, ate so healthy and could never get down to where I needed to be at,” she told People. “I had never taken shortcuts in my career and always worked really hard. I know what it takes to be the best.”