Japan’s Naomi Osaka advanced into the fourth round of the WTA and ATP Miami Open by walkover on Sunday after Serbian Nina Stojanovic withdrew due to a right thigh injury. Second-ranked Osaka, the reigning US and Australian Open champion, will next face the winner of a later match between Belgian 16th seed Elise Mertens and 22nd-seeded Anett Kontaveit of Estonia.

“I’m sorry I can’t continue my participation at the Miami Open due to my recent injury during my singles match,” 95th-ranked qualifier Stojanovic said in a statement.

Osaka, who lifted her fourth Grand Slam title lst month in Melbourne, is seeded second behind top-ranked Australian Ashleigh Barty.