According to this interview he's still recovering from a back injury:

My contract with the UFC has been extended due to my injury. They also expect me to come back, because now a lot of people want to see again in the ring. I come out to fight!, but it all depends on the recovery - concluded Reljić.

The Croatian burst onto the UFC scene at UFC 84 stopping Wilson Gouveia in the second round.  Reljic is undefeated in his career finishing 7 of his 8 opponents.  While he made his UFC debut at light heavyweight, he had plans to move down to middleweight prior to the injury.  He'll be an interesting addition to the middleweight division upon his return.  Which should be sometime this fall if rehab goes according to plan.