After only one season grilling contestants to become healthy and fit, Anna Kournikova has decided to part ways with NBC's hit reality series, "The Biggest Loser."


The 30-year-old tennis sensation joined the training staff earlier this year as part of a refresh for the show's 12th season, a move executive producer Todd Lubin said was about "getting slightly away from just the tape measure, and getting into overall well-being and health."


"You're going to be blown away by how sincere she is, how intense she is, how focused she is for these folks," Lubin told Entertainment Weekly. "She’s totally dedicated to the point where she's getting Bob back into the gym. At one point she breaks down in tears, just because she's so moved by the stories. None of it is fake."


Unfortunately, while Kournikova's background, looks and fitness passion seemed a perfect fit, The Hollywood Reporter says on-set tensions revealed a different story. 


"Staffers say they clashed with her, and some of the contestants found her a bit brash," the site reports. "Whereas Michaels was soothing, encouraging and even uplifting, Kournikova did not sympathize with her overweight contestants, often telling them about her own tough upbringing when they complained about training being hard."


One source told The Hollywood Reporter that Kournikova was simply a "nightmare."


In a statement released to the Reporter, the athlete confirmed the news, expressing nothing but gratitude for the experience. "I enjoyed my time on 'The Biggest Loser' ranch," she wrote. "Although I will not be returning as a 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."


Not everyone was disappointed with Kournikova. "Biggest Loser" contestant Joe Mitchell, who lost nearly 80 pounds before he was eliminated, says she "fixed his thinking."


"Anna made me believe that I could [lose weight]," he told People magazine. "She drilled in our heads that the only person you can really rely on is yourself." 

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Anna Kournikova drops 'The Biggest Loser'
The tennis star who joined the reality weight loss show this year is described as a 'nightmare' to work with.