Dobbins is a good enough player not to be pigeon-holed like that though. Despite Tim's being a banger, he DOES have 4.60 type speed. That gives his some versatility in the system. He was working behind Crowder while Edds worked behind Dansby, but what's happened in the wake of this is that Dobbins is now being shifted over to Dansby's position and he'll probably be primary backup at both spots. With Dobbins shifted over, that leaves the SILB ("Mike") spot open again. While Austin Spitler picks his (freshly surgeried) nose, the Dolphins went ahead and grabbed someone that can be the kind of banger needed to play that vacated SILB spot in practice.