NFL.com lists Isaiah Oliver as a free safety on their website

As you can see in the other screenshots, Oliver is referenced as a safety in the official photos as well. While Alex Lord thought that a move to nickel corner was in the cards for Oliver, he also talked about moving Oliver to safety, and his prediction seems to have come true. Even though Oliver is listed at safety, I expect Dean Pees to use him as a nickel corner and on the boundary on some plays. His versatility will have to shine for him to earn another contract in Atlanta.