The world's number one tennis player, Naomi Osaka, has announced she has split with coach Sascha Bajin.
Osaka said on Twitter on Monday that she was parting ways with the German coach. She gave no details on the decision.
The 21-year-old thanked Bajin for his work and wished him the best for the future.
Bajin replied on Twitter, "I wish you nothing but the best as well. What a ride that was. Thank you for letting me be part of this."
Osaka won last month's Australian Open, her second consecutive grand slam success. The victory elevated her to world number one.
She began working with Bajin in November 2017. He had previously been a training partner for leading players, including Serena Williams.
Under his coaching, Osaka developed a playing style less reliant on physical strength.
He also helped her improve her mental strength and encouraged her to stay positive during matches.
Bajin was presented with the inaugural WTA Coach of the Year award at the end of last season following Osaka's victory at the US Open.