Anna Kournikova will not be returning on the next season of The Biggest Loser.

According to The Hollywood Reporter, some contestants find her unsympathetic and some staffers clashed with her.

The tennis pro-player’s rep said, “Anna was 100 percent not fired from the show.”

Kournikova released a statement saying, “I enjoyed my time on the biggest loser ranch. Although I will not be returning as full-time trainer on Season 13, I will always be a part of The Biggest Loser Family and my commitment to bettering lives through health and fitness will continue.”

A source from from Kournikova’s camp said, “The show was not right fit for her.”

She replaced former trainer Jilian Michael after deciding not to return for Season 12.

Patrick House, who is one of the contestants trained by Kournikova told PEOPLE, “One of the things about The Biggest Loser is that there’s a difference between someone being able to train people versus training overweight people. Bob and Jillian are great at training people versus training obese  people and pushing them to their limits and getting more and more. I think you have to adapt to that and I think that’s what she struggled it.”

Hannah Curlee, also a Biggest Loser alum said, “I think what Anna did was that she never tried to be Jillian . For her that was her biggest achievement. Because no one else is going to be Jilian , no one is going to replace her.”

“Anna came in and tried to carve out her own niche,” Biggest Loser alum Olivia Ward told PEOPLE. “I have to give her kudos for that.”