Blidi is the only lock. New coaching staff likely has different criteria in mind for captains than what we are used to. Based on what I saw from right behind the bench on saturday, the guy most involved in pumping up his teammates was TE Corey Manning.
Masters is a good bet, he is one intense dude and seems well respected around the offensive bench. Nick Williams seems to be liked and respected by everyone also, easily one of the toughest guys on the team. Shoemate is an interesting option, too. He's kind of an "elder statesman" type (assuming he is back: medical Red-shirt??).
On defense, Sio and Joseph/Trevardo are definite possibilities. Stephen is also interesting, although he seems the quiet type. Nobody mentioned Jory Johnson. Seems like he just brings his lunch pail everyday.
For reasons I won't explain here, I don't think Griffin or Junior will be captain. I also don't think McCombs is a candidate: too close to his suspension and he's too cocky on the field. This is still a blue-collar type team and they don't seem to appreciate the showboating.
My dark horse candidate: Gus Cruz