"Manley has taken most of the No. 1 reps through spring and while we have had some great competition, no one has taken those reps away from him at this point," first-year head coach Kim Dameron said.
Manley, a 6-foot-3 redshirt senior who transferred to EIU from New Mexico State last summer, was a backup to Garoppolo a season ago along with junior Ben Krol.
Garoppolo attended Saturday's EIU spring game when Manley completed 13-of-18 pass attempts for 146 yards and two touchdowns in the Blue team's 31-0 victory over the White team.
Krol was 3-of-8 for 68 yards. Two redshirt freshmen also saw action as Austin Green was 7-of-11 for 41 yards and Sean Hussey was 5-of-14 for 42 yards and one interception.
Garoppolo set numerous EIU and Ohio Valley Conference records as a senior, including throwing for 5,050 yards and 53 touchdowns.
EIU had a 12-2 record and a No. 4 final ranking in The Sports Network FCS Top 25, advancing to the national playoff quarterfinals.
The two-time defending OVC champions will open the 2014 season by visiting the University of Minnesota on Aug. 28.