The Rebels suffered an early blow after losing new signing Pauliasi Manu after a neck injury forced the Kiwi to return to Auckland.
The Rebels had high hopes for the former Blues loosehead in 2013 but a failed medical examination has forced Manu home to overcome the disc issue.
Melbourne officials say it was a mutual decision between the club and the 24-year-old, whom they hope to re-sign again next year.
"I'm gutted I'm not going to play for the Rebels next year especially after coming over the first time and meeting the team and management," Manu said.
"The environment was positive and their aspirations were high and I was hoping to be part of the journey next year. We'll see what happens in 2014."
Manu is the second contracted front-rower to have left the Rebels after hooker Ryan Tyrrell returned to Perth this pre-season due to personal reasons.
"Both Ryan and Pauliasi fitted into the Rebels environment well and will be missed, however the end result is in the best interest of all involved," said coach Damien Hill.
"We will remain in contact with Ryan, and hopefully see Pauliasi return to the rugby paddock soon."
With the signing of Japanese hooker Shota Horie for Tyrrell, the Rebels remain one front-rower short.
Nic Henderson and Laurie Weeks are the two experienced props while Eddie Aholelei and Paul Alo-Emile are also under contract following the departures of Rodney Blake and Jono Owen.
A long-time understudy to All Blacks loosehead Tony Woodcock, Manu was instrumental in Auckland's ITM Cup charge this season and started in the team's loss to Canterbury in the final.