Just one week before Bellator MMA is slated to host its first pay-per-view event, the promotion has lost its headliner.

As reported late Friday, lightweight champion Eddie Alvarez suffered a concussion during training and will be unable to defend his title against former title holder Michael Chandler at the May 17 event in Southaven, Miss.

The 30-year-old Alvarez was expected to complete one of the sport’s most exciting trilogies in a rubber match with Chandler. Chandler submitted Alvarez at Bellator 58 in 2011 to capture the promotion’s 155-pound title, but Alvarez got revenge at Bellator 106 last fall and reclaimed his belt.

Stepping in for Alvarez against the former champion Chandler will be season nine lightweight tournament winner Will Brooks. Brooks was originally tabbed to face promotional newcomer Nate Jolly on the night’s main card, but he now moves into the top billing. Brooks and Chandler will battle for the promotion’s interim title while Alvarez recovers from his concussion. Despite the last-minute change, the event will remain on pay-per-view.

Bellator 120 will take place Saturday, May 17 from the Landers Center. The night’s five-fight main card will air live on pay-per-view at 10 p.m. ET. In addition to the Chandler-Brooks headliner, the season ten light heavyweight tournament will be decided as Quinton “Rampage” Jackson takes on Muhammed “King Mo” Lawal. Also, former UFC light heavyweight title holder Tito Ortiz squares off with current Bellator middleweight champion Alexander Shlemenko. The night’s preliminary card will be split between an 8 p.m. ET broadcast on Spike TV and a 6 p.m. ET stream on Spike.com.