the simple answer is that Grimes at least 'was' a very good player ... not just a 'name' like Asomugha or DRC.
the question is his recovery from the Achilles ... if he is healthy and the injury didn't cost him a step -- this is a very good signing. I can only assume that we signed him 1 year based on the unknown ... otherwise, we'd likely have signed him for 2-3.
I honestly don't think Asomugha would have gone anywhere else for the number he got in SF. He's now gonna be surrounded by solid players at every position, which will allow him to maximize his abilities. Which is a pretty smart attempt to save face and show that all the issues in Philly had to do with scheme/personnel.
Grimes plays zone AND man well, and we run a mostly zone defense. Nmandi can't play zone for the life of him, so it'd be a waste. Look at Sean Smith. He was a press corner, and he was awful in our scheme.