Osaka parts ways with coach Bajin

World number one Naomi Osaka has split from her coach Sascha Bajin just weeks after winning the Australian Open to complete back-to-back Grand Slam victories, the Japanese player said Monday.

"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," the 21-year-old tweeted in a shock announcement.

Bajin, a former hitting partner to Serena Williams, 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."

Osaka, who became the first Asian to hold the top ranking after beating Czech Petra Kvitova in the Melbourne final, had worked with the German for just over a year. No reason was given for the decision to part ways.

The Japanese player captured her first Slam by stunning Williams at last year's US Open. Based in the United States, Osaka linked up with Bajin in late 2017 and enjoyed a breakthrough year, climbing from 72 in the world to the top of the women's rankings.

During that period she won the prestigious Indian Wells tournament before scooping her first major in New York, while Bajin was named WTA coach of the year.

Former greats Billie Jean King, Martina Navratilova and Chris Evert have all heaped praise on the new darling of women's tennis.

"Winning back-to-back Grand Slam tournaments is a rare and special achievement, and I'm thrilled these results have propelled Naomi to the top of the women's game," said Chris Evert, the first ever WTA world number one.

"Her exciting brand of tennis, coupled with the dignity she displays on and off court, is a winning combination that tennis fans really embrace."