Well IMO tackling is a must for a DB, if the ball is caught allow no YAC. So if he has the tackling down pretty good then he needs to work on the other aspects, IMO the other things you need field time to get going. Maybe he was thinking too much,trying to get his feet right, his movements etc......IF that is/was the case he may well be what they thought about when picking him.....If he can get to a point were he's playing the game, that's what IMO you would want, that comes with playing time. Now's his chance to do it, he needs to do it.