FWIW the alleged reason that Gibbs wasn't featured more is that he had some fumble issues in camp so they're not 100% convinced he's ready for heavy carries. The knock on him in the draft was he tries to bounce everything outside because of his speed and needed to run more between the tackles. The worst run he had last night was a play where I posted if he cut back left, inside, gaping hole, but he tried to take it outside and got like 2 yards. But he certainly looks like ultimately he's going to be their best RB. He's a much bigger threat as a receiver than Montgomery because he has that extra gear.
It can take awhile for some guys to get comfortable with how big and fast NFL guys are and stop trying to pop everything outside.