What's the most important position in the 3-4 defense?

We have most of the players. Cam hicks bunkley will be a great front 3 lofyon and Hawthorne wil be good inside. Tez will he playing his natural position only thibg I'm worries about is gallettw because I think he is better with his hand in the dirt
If we get a quick linebacker like dion jarvis mingo or ansah we will have a great dront 7