Lopez is an incredible liability with the ball at his feet because (as you point out) he doesn't know what to do with it. However, when he doesn't have the ball, he is generally a tenacious defender (in the mold of the terrier dog biting your ankle) that will run his ass off and has the wheels to do it. PV has obviously decided he'd rather have the defensive help and be a man down on offense rather than the other way around with certain other players.... although as of late, we're a man down on both offense and defense when TMac is on the field, hence his area of the bench has been very warm.