Fellaini is expected to start today at Manchester City.
Carrick said: "We now have other options with Felly. He brings something different to the squad, which is why the manager bought him, and he has done well in the time he's been here. Against Leverkusen he was brilliant.
"Now, it's the big one against City and it's in these types of games that you want as many forceful players as possible in the side.
"With Tom Cleverley and Anderson also in there, it's tough for the manager to pick his midfield."