The fight headlines Bellator 66, which will be held at the I-X Center in Cleveland.
Alvarez has sought the fight since suffering a first-round submission loss to Aoki in December 2008.
"I promised Eddie I would put this fight together three years ago," Rebney told ESPN.com. "When Eddie lost (to Aoki) he and I had first started working together.
"This fight is incredibly important to Ed. It's hard to overestimate the importance of this fight for Eddie Alvarez right now."
Alvarez (22-3) will enter the cage for the first time since losing his title Nov. 19 to Michael Chandler at Bellator 58. Chandler won the bout by unanimous decision.
A victory would strengthen Alvarez's position for a rematch with Chandler.
"If he wins (this fight) he reopens the door to get right back on track to where he was at the time he lost to Chandler," Rebney said. "If the opposite occurs, it's not a good loss."
Aoki, the Dream lightweight titleholder, has won seven fights in a row since dropping a unanimous decision to current Strikeforce champion Gilbert Melendez in April 2010. He has a professional record of 30-5 with one no contest.
Franklin McNeil covers mixed martial arts and boxing for ESPN.com. Follow him on Twitter at www.twitter.com/Franklin_McNeil.