He makes a hell lot of difference to the new-look United. Whenever he plays, United attacks are swift and ferocious. Whenever he's restd, United looked sluggish and out of ideas.
Observe his gameplay in United's matches and you'll notice that Carrick is always in the centre of every United attacks. His uncanny ability to spread the ball across the field is one of the best. He does his fair share of track back as well and luckily for us cos he doesn't make mistimed challenges like Scholes did.

Glory Glory Man United~
Cheers.
CK