Sebastien Grosjean has quit as captain of France's Davis Cup team to coach young French hope Arthur Fils, the country's tennis federation announced on Monday.
"After leading the French team with passion and determination for four years Sebastien Grosjean has decided to resign to concentrate on a new mission. He becomes, from today, the personal trainer... of Arthur Fils," the federation reported.
Fils, 19, won his first ATP title in Lyon this season, and on Sunday was beaten in the final at Antwerp by Alexander Bublik.
"It's with a great deal of emotion but also lots of excitement that I'm ready to start this new chapter with Arthur Fils," said Grosjean.
The former world No 4 took over the Davis Cup captaincy from Amelie Mauresmo in 2018.
In July the federation kept him in his role but removed his power to select his team to avoid any potential conflict of interest "resulting from his outside activities".
His replacement will be chosen next week.