At Safety the depth is a bit better than you might think because there were so many players out at that position with injury this year. Even with the losses of Ingol and Kristoff, and probably Carpenter, you return:
Devin Jones R-Sr (started 7 games, played in 8 in 2014, played in 8 in 2013)
Aaron Macer R-Sr (played in 10 games in 2014, and ten in 2013)
Toran Davis R-Jr (started 2 games, played in all the others, played in 10 in 2013)
Blake Scipio R-Jr (saw limited action in 4 games, missed all of 2013 with injury, but played extensively in 2012)
Corey Quallen R-So (played in the first 3 games before a toe injury)
Grant Cunningham R-So (played in 9 games)
In addition to these, Carpenter has applied for a 6th year, and might play.
Could we see Hagan or M. Williams playing as a true freshman at Safety? Sure, it could happen.
What about DT? I would think we will not see any of the true freshmen there. They will all benefit from a redshirt year. I expect Tautuaiki and Purdum will start, and that Porter and Aloese will be the backups.
Kuhar should get a look at DT, plus any other of the DEs who find themselves gaining weight. they don't call it the "freshman 15" for nothing.