Melbourne - World number 11 Grigor Dimitrov has split with coach Roger Rasheed, days after his disappointing third-round exit from Wimbledon.
The Bulgarian confirmed the move on Twitter.
"After much thought I have decided to end my working relationship with Roger," the 24-year-old tweeted.
"We had many accomplishments together and I wish him all the best going forward."
Long touted as a future Grand Slam champion, Dimitrov began working with Rasheed in 2013 and made the semi-finals at Wimbledon last year on the way to cracking the top 10 in a breakout season under the Australian.
However, the high-profile boyfriend of Maria Sharapova has hit the wall this year, crashing out of the French Open in the first round before being dumped in straight sets by Frenchman Richard Gasquet at Wimbledon.
Dimitrov made no mention of his future coaching direction but in the Wimbledon wash-up expressed frustration at his form and suggested changes were afoot.
"I'm 24, I don't consider myself that young any more," he said after his Gasquet loss.
"Last year was an eye-opener for me, it showed me what I was capable of. I fell into a rhythm that I always wanted to, but I always knew it was very hard to sustain.
"Especially this year, I've had quite a few difficulties to cooperate with the situation that I'm not playing as good as last year.
"It comes down to a bit of mental strength, something that you really need to sort of look at it and maybe see what you can do different."