World number one Naomi Osaka has announced an immediate split from her coach Sascha Bajin. The 2019 Australian Open champion didn’t give any reason for the split from Bajin, who was named WTA coach of the year in 2018.

The Japanese player has enjoyed a remarkable rise up the world rankings after first linking up with the German in the 2017 off-season.

Osaka rose from 72nd to reach the top five during the course of 2018, culminating in her maiden Grand Slam success at the US Open, when she gunned down Serena Williams in the decider at Flushing Meadows.

She made it back-to-back major successes in Melbourne last month, defeating Petra Kvitova in three sets in the final.

Osaka tweeted: “Hey everyone, I will no longer be working together with Sascha. I thank him for his work and wish him all the best in the future.”

While details of the split remain in short supply, it appears it was an amicable one. Bajin soon responded: “Thank you Naomi I wish you nothing but the best as well. What a ride that was. Thank you for letting me be part of this.”

The news will have come as a shock for many in the women’s game as it was just six months ago that Bajin suggested he was “in it for the long haul” with rising star Osaka.

Osaka is 9.50 to make it a hat-trick of Grand Slam titles by winning the French Open in Paris this spring.