The moment was caught in a gif that was put together by Bloody Elbow video reporter Zombie Prophet.
Fight fans who want to know why Rebney would shake his head after Alvarez won Bellator's lightweight belt should think about the circumstances behind the champ's victory.
Of course its just speculation, but Rebney may not be happy about Alvarez being one fight closer to leaving with the belt. Alvarez had a lengthy contract dispute with Bellator, so no one knows for sure where he stands with the promotion.
Michael Chandler is the face of Bellator and will likely be part of the promotion for the long haul, but Alvarez may head to the UFC sometime in the near future.
Chandler was supposed to be an unbeatable homegrown champion and someone who could carry Bellator into a bright future, but he was beaten by someone who may not be with the promotion for much longer.
For what its worth, Rebney might not have actually been shaking his head in disappointment with Alvarez's victory.
The crowd on hand for Bellator 106 was booing, so it's quite possible that Rebney was simply frustrated by emotional response the event's attendees, who had just witnessed a great fight.
After all, Chandler vs Alvarez II was an epic battle that will undoubtedly be a "Fight of the Year" contender, so Rebney couldn't have been pleased with the boos emanating from the crowd.
Rebney hasn't issued any official statement on why he shook his head after the victory, so that leaves MMA fans speculating about it on various forums.
Rebney doesn't have to worry about Alvarez leaving just yet, as he's locked in for at least one more Bellator fight.
"I think part of the magic that they were able to create tonight was based on the fact that Ed had a long period off and was able to heal and recreate what he does," Rebney said. "Michael got a lot of time off, and Michael had a couple of title defenses, but they were short-order title defenses (in which) he took no damage. But [the rematch is] the kind of fight that you're going to need to take some time off. Once they're both back at 120 percent, there's nothing in the way of doing No. 3."