Monte Carlo - Dominic Thiem confirmed on Sunday's opening day of the Monte Carlo Masters that he has all but split from longtime coach Gunter Bresnik.
The 26-year-old who played the 2018 French Open final against Rafael Nadal and won the Indian Wells Masters title on hardcourt a month ago for a career breakthrough, explained the parting of ways.
"We've been together 15 years, he will stay on my team - but tennis-wise, it's over."
Reports in Austrian media had been circulating for months concerning the strained relationship between a mentor tired of travelling the circuit and a rising-star pupil.
Thiem worked for a time with Galo Blanco as travelling coach, but last year the Spaniard joined the new Spanish Davis Cup organiser Kosmos.
2004 Athens Olympic champion Nicolas Massu began working with Thiem in February at South American events and was on board for the Indian Wells trophy success.
"We had some great training before Indian Wells," world No 5 Thiem said.
"We achieved a title and have a great relationship.
"He has added many good things to my game. he also grew up on clay, which is my favourite surface.
"I'm expecting good things to happen."
The Austrian is prepared to aim for the starts in the spring run-up to Roland Garros.
"I expect a lot on clay, like I do every season; these are strong events for me.
"The draw here is so strong and the level of tennis is very high at the moment.
"We all have to be full power on from first point of every match."