Important goals, chest trap to die for. Aside that he's not a guaranteed starter, he's a squad player.
When we replace Carrick he's only cover for Herrera & Pogba.
We seem to play with 3 CMs in most games and Fellaini gets a crap load of starts. He's above "squad player" status at the moment for me. Young is a squad player.
If Carrick is replaced with a DM who gets a starting XI spot next to Herrera and Pogba, then the next MF in line (whoever that guy is, whether it's Keita or Fellaini) will still get a huge amount of games, probably as many as the other 3.
That MF might not be starting the most important of fixtures, barring injuries and suspensions of course, but still loads of games. Enough for any young player to be content at a big club.
Fellaini is entering the final year of his contract with no extension option (already used up), so he either gets offered a new deal in the summer or he's sold. In either case my ideal scenario would be for him to be 5th option behind Pogba, Herrera and two new arrivals. We lost 2 MF'ers this season (Schweini and Morgan) and have been a bit light in that department with Herrera and Pogba having started too many back to back games due to our lack of numbers. We're also about to lose another MF in Carrick. So we do need 2 arrivals minimum, and whether 1 of them will be Pereira or whether we'll need to buy 2 new CMs, remains to be seen.