Maria Sharapova has "mutually agreed" to part company with her coach of four years, Sven Groeneveld.
Groeneveld started working with Sharapova in 2014, and helped her to win the French Open that season.
The pair remained a team during the Russian’s 15-month doping ban for taking meldonium in 2016.
But the 30-year-old Russian has won just five matches this year, and was beaten in the first round at Indian Wells this week.
Sharapova said the pair had enjoyed "four successful and challenging years of collaboration".
"Although we have mutually agreed to part ways during this time, I have been incredibly fortunate to have a team leader like him in my corner for the past four years," she added.
The Dutch coach has previously worked with players including Monica Seles, Arantxa Sanchez Vicario, Ana Ivanovic, Caroline Wozniacki and Britain’s Greg Rusedski.
"Maria has been one of the most hardworking and professional players I have ever worked with and I have the deepest respect for her as a player and person," he said.