CNN  — 

British tennis star Emma Raducanu says it was a “tough” decision to split with coach Torben Beltz after only five months together.

The 19-year-old, who stunned the tennis world by winning the US Open as a qualifier last year, is now searching for a fourth coach in less than year.

Raducanu’s split from the German came as a surprise to many as she continues her buildup on clay ahead of her first French Open appearance next month.

“Torben is a very great guy,” she told reporters ahead of this week’s Madrid Open. “I really enjoyed my time with him on and off the court.

“He is one of the nicest people I’ve met, so obviously it was a tough one to split with someone like that, but I feel like right now I’m very comfortable with my current training.

“Torben has been great for me because when I wanted someone with tour experience, I think for my first six months on the tour, it was very valuable.”

READ: Emma Raducanu voted BBC Sports Personality of the Year

Emma Raducanu with Torben Beltz at Indian Wells.

Raducanu reached the quarterfinals of last week’s Stuttgart Open – her first career WTA 500 quarterfinal – but lost in straight sets to world No. 1 Iga Swiatek.

However, it marked a significant improvement on her difficult start to the year, during which she suffered a number of first round exits to lower-ranked opponents and also dealt with injuries.

“Going forward, I’ll probably be putting a lot more emphasis on sparring,” Raducanu added.

“It’s becoming more apparent to me, as I spend more time on the tour, it’s just getting used to these girls’ ball speed.

“I like to mix it up. I like to work very specifically and I’m very clear on what I want to work on. A lot of the time those ideas come from myself.”

Raducanu faces Czech world No. 49 Tereza Martincova in the first round in Madrid on Friday.