Emma Raducanu sacked coach Vlado Platenik by phone the night before her first-round win at the Miami Open.
The pair had been working together for just two weeks, with their trial period originally expected to last until the French Open in late May.
Platenik was notably absent from the British star's box during her victory over Sayaka Ishii on Wednesday.
Raducanu's management announced they had split because the partnership was not "heading in the right direction".
Emma Raducanu has changed coaches again
PADespite the split, Platenik spoke glowingly about Raducanu's potential and progress.
"I never had a player who improved as fast as Emma," the Slovakian told The Telegraph.
"We had a hard but good eight or nine days of practice," he added.
Platenik, 49, was understanding about the sudden termination, saying: "Emma said she wanted to pause the collaboration. I understand that she is under a lot of pressure and it's not easy for her, so I respect her decision."
The Slovakian coach detailed specific technical improvements they worked on during their brief collaboration.
"We worked a bit differently than she was used to, improving a lot specially on footwork positioning," Platenik explained.
JUST IN: Jake Paul lists three reasons why he could knock Anthony Joshua
He also focused on her serve technique, noting: "We improved the serve with higher toss, and worked a lot on second serve where she also had a bad toss."
"Now she can use the kick-serve more and be more aggressive even on second serve."
Platenik was optimistic about Raducanu's future in the sport despite their brief partnership.
"If she can keep stabilising those things we were working on, she can get back into the world's top 20," he told The Telegraph.
However, he was careful not to set limits on her potential.
READ MORE: Max Verstappen faces F1 ban ahead of Chinese Grand Prix - alongside another driver
Emma Raducanu called Vlado Platenik the night before her Miami Open match
Reuters
"If a girl is working there are no limits: look at Mirra Andreeva," he said, referencing the 17-year-old Russian who recently won tournaments in Indian Wells and Dubai.
Raducanu's decision to dismiss Platenik so swiftly has revived discussions about her approach to hiring and firing coaches.
This marks the eighth coach of her career, coming after she had spent 13 months working with childhood ally Nick Cavaday.
Ironically, Platenik had previously described working with Raducanu as "coaching suicide" in a Slovakian interview.
Raducanu has previously attributed her coaching turnover to coaches being unable to "keep up with the questions" she asks.
LATEST SPORTS NEWS:
Emma Raducanu defeated Sayaka Ishii in the first round of the Miami Open
Reuters
In the absence of Platenik, Raducanu is now working with LTA coach Colin Beecher and her childhood coach Jane O'Donoghue in Miami.
The British star faces a tough challenge in her next match at the Miami Open.
She is scheduled to play against American eighth seed Emma Navarro in the second round on Friday.
Raducanu had made an upbeat start to the tournament with her victory over Sayaka Ishii, where she looked thoroughly in control of her service games.
