If the team is only throwing to the RB's, or the RB's and a TE, then here is what you need to do. Since he is ignoring his WR's you can also ignore them, so blitz with your CB's on every down. You need to use at least as many LB's in coverage as he has receivers in the pass pattern, therefore if he is passing to 2 RB's and a TE you need at least 3 LB's in cover. Do not blitz with your FS or SS, they are backing up your LB's deep. If your opponent does not leave an RB, or at least a TE in to help with blocking and he tries to throw long or deep, then you are going to rack up a lot of sacks with your CB blitz. If he is throwing all short passes or short to medium passes, then move your DB's up closer to the line and you will probably get some coverage sacks. If he decides to start throwing to his WR's then you may give up some yards but your FS and SS's will cover for the blitzing CB. That's what I did and it worked for me in a 3-4 defense and it should also work in a 4-3, you would have to be careful in a 4-4 if he is throwing deep to multiple receivers.