In what has been one of the biggest shocks of 2019, Naomi Osaka announced that she will no longer be working with coach Sascha Bajin.

The move bewildered many because of the Japanese player's recent success. Following her lack of big wins in 2017, ending the year No. 68 in the world, Osaka hired Bajin—the former hitting partner of Serena Williams. The partnership started one of the greatest rises in recent years, as she rose to world No. 1 after winning Indian Wells and two Grand Slams in a row.

No one knows exactly why the two split yet, but, for Osaka, she's got to focus on defending her title in Indian Wells. Can Osaka continue her dominance without Bajin?