They gained more than they lost.
The best player lost was Mike Jenkins and he was the 4th option at CB when everybody is healthy. Felix was the 2nd best player lost but he was fat and out of shape last year. Sensabaugh had a lot of experience but was never a very good player.
Now:
Healthy: Costa, Kowalski, Church, Murray, Ware, Ratliff, Lee, Carter, Scandrick, Matt Johnson...
Maybe Healthy by game 1: Bernadeau, Livings
Added (draft): Frederick, Escobar, T. Williams, Wilcox, Webb, Randle, Holloman, UDFAs Magee, etc..
Added (FA): Durant, Allen
More mature/experienced: Parnell, Leary, Matt Johnson, Carter, Hanna, Crawford, Wilber, Bass, Lissemore, Claiborne, Albright, Dunbar, Harris, Church
Full off-season with the team: Sims
D-Coordinator: Ryan out, Kiffin/Marinelli in
Assistant OL coach: Phillips replaced by Pollack
Other possible upgrades on coaching staff: Bisaccia, Dooley, Brown
Other possible improvement: Callahan calling plays from the booth, Garrett with more focus on the overall game