Australian Open Champion Naomi Osaka has announced a surprising split with coach Sascha Bajin to abruptly end their momentous 13-month partnership.
She also thanked Bajin and wished him "all the best in the future".
"Thanks to my team, I don't think I would have made it through this week without you", she said after her Australian Open triumph.More news: Apple's Rough Quarter in China Hit iPhone Sales Hard
She became the first Asian to hold the top ranking after downing Czech Petra Kvitova in a tight final in Australia after beating Serena Williams in a memorable US Open final a year ago in which she won many fans for her grace under pressure.
Osaka became the youngest woman to make her debut at No. 1 since Wozniacki at 20 in 2010 and the first tennis player from Asia to reach the top of the women's or men's tennis rankings.
That added to her championship at the U.S. Open last September, when she defeated Serena Williams in straight sets.More news: Beijing expresses anger at US Navy mission through disputed South China Sea
Less than a half-hour after Osaka's tweet, Bajin responded to her on Twitter.
"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.
Former greats Billie Jean King, Martina Navratilova and Chris Evert have all heaped praise on the new darling of women's tennis.More news: Coach Warren Gatland warns no-holds barred as Wales target record