"He doesn't look out of place," Devils coach Pete DeBoer said after the team's intra-squad scrimmage on Wednesday.
Matteau, 18, will wear No. 15, according to the Devils. Per the rules for the lockout-shortened 48-game season, Matteau will have six games to prove he belongs before the Devils have to make a decision on whether to keep him with the big club or send him back to his junior team.
The Devils open the season on the road against the Islanders on Saturday at Nassau Coliseum.
In order to make space on the roster, injured center Adam Henrique (hand) was assigned to Albany (AHL).