Andrew Richardson coached Raducanu for two years at youth level and linked up with her again in July on a short-term deal for the duration of her time in the United States ahead of and during the U.S. Open.
The 18-year-old from England said on Friday she wants a more experienced coach now that she will be playing in bigger events on the WTA Tour.
"I'm looking for someone who has been at that level and knows what it takes," Raducanu said.
"And especially right now because I'm so new to it, I really need someone to guide me who's already been through that."
Richardson is a former Davis Cup player for Britain but has little experience of the WTA Tour.
"At the time, I thought Andrew would be a great coach to trial so we went to the States but never did I even dream of winning the U.S. Open and having the run I did," Raducanu said, "and now I'm ranked No. 22 in the world, which is pretty crazy to me."
Raducanu said she didn't have a coach in mind to replace Richardson and does not expect to make any decision until the end of the season.
Raducanu is back in training after taking some time off following the U.S. Open and is weighing up when to return to the tour, with the BNP Paribas Open in Indian Wells -- one of the biggest events on tour -- starting on Oct. 6.
"I'll decide in the next few days where I'm going to go to but, wherever I play next, I'm going to make sure I'm ready," she said. "I don't want to jump into things too early."
Raducanu played with the Duchess of Cambridge, the patron of the Lawn Tennis Association, at a homecoming event on Friday.
Asked if she had more nerves playing Kate or her U.S. Open final opponent Leylah Fernandez, Raducanu said: "I was actually very nervous playing the duchess -- I was like, 'Don't miss, don't miss.'"
Raducanu, who ended Britain's 44-year wait for a women's Grand Slam champion, said Kate's forehand was "incredible."
"I was very impressed. It was a lot of fun to play tennis with the duchess," Raducanu said of the event hosted by the LTA Youth program at the National Tennis Centre outside London.