A replacement opponent will be needed for BJ Penn’s return to competition.

According to BJPenn.com, Dennis Siver has suffered an undisclosed injury and subsequently withdrew from his upcoming bout against the all-time great. The two were expected to face off in just over three weeks at UFC 199 in Los Angeles.

Penn, 37, announced in January that he would be coming out of retirement to make a run at the 145-pound title. To prepare for his return, Penn moved camps to Albuquerque, NM to train under Greg Jackson alongside the likes of Jon Jones, Holly Holm, and many others. His last bout was against Frankie Edgar in 2014 where he suffered a brutal third-round TKO loss after which he announced his retirement.

The UFC has not released any official announcements regarding Siver’s injury but it is likely that a replacement will be found.