I would keep,
Willis and Mays on "D". Due to age and play making ability.
V. Davis and Crabtree, you need to keep the dynamic Davis, for his leadership qualities and his prowess. Crabtree, will be deadly in the West Coast offense that Harbough will implement. TRUST ME! FACT - Did you know when Davis found out Jim was the HC he jumped into the hotub fully clothed? lol. IT'S TRUE.