Essentially Schneiderlin can replace Carrick as the position isn't defined by Carrick.

I'd say that they're pretty similar players apart from a few differences.

I've always thought of Schneiderlin as a more box to box type of player whereas Carrick isn't synonymous with doing that apart from when he turned into Messi against QPR a few years back.

Carrick relies more on positional sense to win balls back and when defending his positioning is usually great whereas Schneiderlin puts a lot of tackles in.

Carrick is a far superior passer he can hit a dime from 30 yards or start attacks with balls around the corner, Schneiderlin can pass but nowhere near Carricks level in my opinion, but he has it in his locker.

But again I don't think there's a massive amount of difference between them. Until you watch them and notice that what Carrick brings to the game is better than what Schneiderlin brings.

Note: I should also note, in terms of Schneiderlin what I'm remembering is from his time at Southampton as let's face it there's not much to go by as a United player. Playing for Southampton is a lot different to playing for United in terms of how the opposition set up and how much time you have on the ball.