I asked the same thing and couldn't find an answer. I'm wondering about Dez Jackson as well, although I heard he was banged up early I'm camp. Next week would be a great time for them to get some reps.
If I were Gundy, I don't think I'd show off Jeter right now. Chuba and Brown need to get up to speed and the physical demands of the season pronto. Plus, Chuba is a legit candidate for some high profile attention. He, Wallace and Sanders need the PT.
I'd wait to showcase Jeter down the line after he's had more practice and the season starts banging some people us a bit. When they need a little rest, then bring in the unknown diamonds-in-the-rough.
Chuba has good vision and finds holes if available to him, Brown is good if no one is anywhere near him and he is a blazer. Unfortunately he isn't a back that will make his own opportunities. Not sure leaving him at 2 is a good option.