Surprise U.S. Open champion Emma Raducanu announced she is splitting with the coach that helped her win the grand slam tournament.

During an event in London, with the Duchess Cambridge, Raducanu said that she decided to look for someone with more experience.

"I feel like at this stage in my career, and playing the top players in the world, I realized I really need someone right now that has had that WTA Tour experience at the high levels, which means that I'm looking for someone who has been at that level and knows what it takes," Raducanu said, according to CNN.

Raducanu's previous coach, Andrew Richardson, joined rejoined her team this year. He had reportedly worked with Raducanu as a young girl.

Raducanu said she has not chosen a new coach yet.

The 18-year-old became the first man or woman to win a grand slam tournament as a qualifier. Prior to the tournament, she was ranked outside the top 200.

After the win, she shot up to No. 22 in the world.