Dmitry Tursunov says “red flags” convinced him to stop coaching British number one Emma Raducanu.
The Russian says he advised former US Open champion Raducanu, 19, and her team that she needed to listen to “one voice”.
Tursunov, Raducanu’s fourth coach in 15 months, said: “I felt like there were going to be problems later.”
Raducanu won eight of 15 matches alongside Tursunov before their split two weeks ago.
“We didn’t agree on the terms and there were some red flags that just couldn’t be ignored,” 39-year-old Tursunov told tennismajors.com
“She’s probably a two-and-a-half-year project. Her game is very raw.
“It’s going to take some time, but as I said to her and to pretty much everyone on her team, ‘I think you just need to have one voice and just try that for a bit’.”
Raducanu shocked the tennis world with her victory at the 2021 US Open, becoming the first qualifier in the Open era to win a Grand Slam and the first British woman in 44 years.
She was unable to build on that success in her first season on the WTA Tour as she struggled with injuries and changed coaches.
Raducanu has worked with Britons Nigel Sears and Andrew Richardson, but has been without a full-time coach since parting with German Torben Beltz in April.
She began working with Tursunov on a part-time basis after losing in the second round at Wimbledon this summer.
The trial with Tursunov was due to finish after the US Open – Raducanu was knocked out in the first round – but they remained together for a further month.
In that time she reached the Seoul Open semi-finals, her first on the WTA Tour since her US Open victory.
“I could have stuck around, I could have agreed on everything that her team proposed, but, deep down, I felt like that wasn’t the right thing to do,” said Tursunov, who previously helped Belarus’ Aryna Sabalenka break into the world’s top 10 and now works with Switzerland’s Olympic champion and world number 13 Belinda Bencic.
“She’s absolutely great, she’s a hard worker and she doesn’t think or act like she’s a superstar,” Tursunov said of Raducanu. “She is hungry to improve and is obsessed with tennis. It’s quite a rare combination.
“So I really loved working with her, and I really wanted to make it work. It was a very difficult decision for me to walk away from a player that I like and respect.
“I felt it was going to be an interesting project. I was really hoping to find a solution to continue, but, in the end, we just couldn’t agree on the terms so I had to leave.”
BBC Sport has approached Raducanu for comment.
She is due to lead the Great Britain team in the Billie Jean King Cup finals in Glasgow in November.