He's never played nickel as far as I can tell. Nickel corner and outside are two very different positions. Many guys that play outside can't play nickel. And there's definitely guys at nickel who can be abused on the outside. When we lost Troy Hill who had inside/outside versatility to play both, we moved Williams part time to nickel and it was a disaster. We eventually moved him back to outside corner full time.
Whereas length and speed are great to have at the outside, quickness/agility (there's no sideline, they have to be able to quickly react in any direction), awareness (so many different ways to attack a nickel with choice routes, run at them, picks, etc), and tackling are a premium inside at nickel.
You can't just place a guy there and sometimes you have to split the responsibilities ala Lake as a big nickel where you give up some of the quickness/agility for length and size in defense of big slots and the run.
Now we have White on a 1 year contract and sounds like we're not rushing him back. You can still make an argument for picking him for the future (I'm not sure it's great depending on other talent avail) I just don't see a compelling argument that he can play nickel.