Ever since Athing Mu-Nikolayev turned professional after college in 2021, one person has always been by her side: her coach, Bobby Kersee. Together, they achieved some solid results – in 2023, she won a bronze medal at the World Athletics Championships and set the American record in the 800m with 1:54.97. Mu’s star was rising, but in 2025, things changed.

After a season of highs and lows, including missing the 800m final at the U.S. Championships, the double Olympic champion made a big decision regarding her future. She parted ways with Kersee, ending their 3-year partnership. Kersee confirmed the split with Let’s Run’s Jonathan Gault, saying Mu-Nikolayev informed him of her decision in September, just before the World Championships in Tokyo.

“She got married [in March to Russian athlete Yegor Nikolayev],” Kersee explained. “Her and her husband were looking at a situation in Dallas. We met [before Worlds], and I didn’t have any animosity or anything like that. It was just a life decision.”

Following the split, Mu-Nikolayev and her husband moved from Los Angeles, where she had trained under Kersee, to Dallas. But this move has sparked curiosity among fans and analysts: who will guide her next?

So far, Athing Mu-Nikolayev has not announced her new coach or detailed her future training plans. Even after the professional separation, Kersee spoke highly of Mu-Nikolayev. “Once she’s healthy… she’s going to be very hard to beat. She’s that talented,” he said. “It was a blessing for me to coach her. I enjoyed coaching her. I loved her attitude, I loved her support. There’s nothing whatsoever I regret.”

But the question arises, why did Mu-Nikolayev leave the coach? Well, nobody knows as she hasn’t publicly explained her decision. Many speculate that missed opportunities and a desire for a fresh start may have played a role.

Could missed opportunities have led Athing Mu-Nikolayev to leave her coach?

When Athing Mu-Nikolayev joined Bob Kersee’s camp in 2022, she was already one of the brightest stars in track and field. She had Olympic and world titles in the 800m under her college coach, Milton Mallard, and was seen as one of America’s top middle-distance runners. It started with her relocation from Texas and joining Kersee’s training group in LA with other elite athletes. But her first year with Kersee in 2023 had both ups and downs.

She raced only a few times and even thought about skipping the World Championships. In the end, she competed and earned a bronze medal, the first professional loss of her career. And then, she ended the season on a high note by winning the Diamond League title at the Prefontaine Classic and setting a new American record in the 800m with 1:54.97.

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At that time, Mu-Nikolayev said, “Bobby is so good – he is such a great coach. If I do need to change coach again, all I’d be doing is downgrading – and I can’t really do that. So I’m probably going to be here for a while, as Bobby is the greatest coach of all time.”

Bobby Kersee has a legendary resume, having coached some of the best talent in the sport, including Allyson Felix, Jackie Joyner-Kersee, and Sydney McLaughlin-Levrone.

Later that year Kersee entered Mu-Nikolayev into the 1500m at the U.S. Championships. Even though the move invited criticism since she was mainly a 400/800m runner, she finished second, sparking talk about a possible 800/1500m double at the 2024 Olympics.

But 2024 didn’t go as planned. A torn hamstring before the Olympic Trials derailed her hopes, and a fall just 200 meters into the final ended her Olympic dreams. A far cry from Tokyo 2020 when she walked away with two gold medals.

Her struggles persisted in 2025. She dealt with niggling injuries all season long, competing in just two races – a low-profile 1500m at Track Fest, and the 800m at the Prefontaine Classic. But even though the last two seasons have been challenging for Mu-Nikolayev, at 23, she has a long future ahead of her.

While the injuries, some blown chances, and need for a fresh start likely came into play in her decision to switch coaches, one thing is clear: Athing Mu-Nikolayev’s next chapter has the potential to be her most thrilling one yet.