The Cowboys struggled on defense last season due to several injuries to key players, and Carter in particular had trouble holding his own in the middle because of the absence of Sean Lee.
Marinelli told ESPN: "I don't do confidence stuff. Get down and play. Get down and play. Here's your assignment key. We want you to play fast and we want you to take the ball away.
"Go play. It's a man's game, man. Play it the right way. That's what I want. We're going to coach it. We'll coach you hard. Be where you're supposed to be. This is what we expect. And then go."
Carter recorded 96 tackles and two sacks for the Cowboys in the 2013 season.