Former world number one Maria Sharapova said on Friday she had split with her coach Sven Groeneveld, two days after losing a third consecutive match for the first time since 2003.
The news comes after Sharapova, who said the decision to end their four-year partnership was "mutually agreed", was beaten by 44th-ranked Naomi Osaka in the first round of the BNP Paribas Open in California on Wednesday.
After losing in the third round of the Australian Open to Angelique Kerber she was then beaten in the first round of the Qatar Open by Romanian qualifier Monica Niculescu.
She pulled out of the Dubai Duty Free Tennis Championships.
Sharapova has struggled to recapture top form since her 15-month ban for taking the banned drug meldonium ended last April.
"After four successful and challenging years of collaboration together, I would like to thank Sven for his incredible loyalty, work ethic and most importantly the friendship that we have formed that will go beyond this working partnership," Sharapova said in a statement on her website.
"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."
Russian Sharapova won seven titles during her time with Groeneveld, most notably the 2014 French Open.
A two-time champion at Indian Wells, Sharapova, currently ranked 41st in the world, won the Tianjin Open in October for her first triumph since returning to the WTA Tour, but has not come close to challenging for a tournament victory since.
"Maria has been one of the most hardworking and professional players I have ever worked with," Groeneveld said.
"Her strength and fighting spirit will continue to be a force to reckon with and I have the deepest respect for her as a player and person.”
IMAGE: Maria Sharapova has a drink break during a practice session
Photograph: Michael Dodge/Getty Images