I'm with Fish, Joe. Not sure what you are concerned about---looked to me vs. Florida that when he tackles someone, they GO DOWN and stay there. And he gets on them so quickly he makes more tackles than our "traditional" linebackers...which obviously excepts Gold and Jones, who also had great speed.
My only concern about D.B. is his propensity to commit personal fouls...again, a by-product his great speed and desire to use it at all times.