Despite an apparent winning formula on court, Osaka has split with German national Bajin, although the twenty-one-year-old player did hint the two had amicably parted ways.
"Hey everyone, I will no longer be working together with Sascha", Osaka said.
There was a sense of shock as Naomi Osaka announced on Monday night that she had split from her coach Sascha Bajin, just 17 days after completing back-to-back Grand Slam victories at the Australian Open. "Thank you for letting me be part of this" he tweeted.
Bajin won't take long to attract new suitors - he has previously worked with Williams, Victoria Azarenka and Caroline Wozniacki.
Along with her accomplishment in NY, the 21-year-old continued to keep her Grand Slam winning streak to be unbroken in Australia and became the tenth women in the history tennis to consecutively win the U.S. Open and Australian Open.
Some fans pointed out that she had not named him in her speech after her win at the Australian Open.
The Japanese player climbed from world No.72 to reach the top five during the course of 2018, when she won her first grand slam title, and then hit top spot after her success in Melbourne.
She was born in Japan - her mother is Japanese, her father is Haitian - and moved to the United States when she was 3.