Rebels taking no risks
McGahan named a 24-player team, which includes 11 uncapped players for their first competitive fixture of 2016 against the Blues on Thursday.
The team includes a combination of Rebels, extended squad players, Under-20s and local Melbourne players.
"We want to test our extended squad members in a competitive environment, so this trial against the Blues will give these players a chance to put into practice our last eight weeks of pre-season training," said McGahan.
"These players have all earned their opportunity through hard work during pre-season so I want them to back themselves and their decision making under pressure in a game situation.
"At this stage of pre-season there's bound to be a few bumps and bruises in our squad," McGahan said. "We're not prepared to take any risk with three weeks until the start of the season but we expect to have a near full strength team available for our trial against Samoa."
New recruits James Hanson and Reece Hodge, along with Melbourne Rising player Sione Taufa and U20 member Ta Hosea, will pull on a Rebels jersey for the first time after being named in the starting line-up.
The Rebels team for the first trial will feature 12 players returning from last season and 603 Super Rugby games of experience, led by foundation team members Laurie Weeks and Luke Jones.
The backs will feature some familiar faces with Jack Debreczeni, Tom English, Mike Harris, Mitch Inman and Dom Shipperley, who were all in the starting line-up in the Rebels 42-22 victory over the Blues the last time these two sides met at AAMI Park in 2015.
Melbourne Rebels: 15 Reece Hodge, 14 Dom Shipperley, 13 Mitch Inman, 12 Mike Harris, 11 Tom English, 10 Jack Debreczeni, 9 Ben Meehan, 8 Ta Hosea, 7 Sione Taufa, 6 Jordy Reid, 5 Luke Jones, 4 Steve Cummins, 3 Laurie Weeks, 2 James Hanson, 1 Toby Smith.
Replacements: 16 Jordon Uelese, 17 Cruze Ah Nau, 18 Ryan Cocker, 19 Murray Douglas, 20 Pom Simona, 21 Angus Fowler, 22 Dan Hawkins, 23 Paul Asquith, 24 Tom Moloney.
Date: Thursday, February 4
Venue: Pakuranga Rugby Club
Kick-off: 15.30 (17.30 NZ time; 4.30 GMT)
Referee: TBC