Yoshihito Nishioka will undergo surgery for a torn ACL next week.
The 21-year-old from Japan experienced the injury in Miami, retiring from his second-round match. He was coming off a fourth-round showing in Indian Wells, breaking into the top 60 in the rankings.
"I am disappointed with this news, but will do everything I can to come back even stronger," he wrote on social media.
Nishioka is the second-highest ranked Japanese player on the ATP tour, behind Kei Nishikori.