Walker is not suited to play NT because his game is more like a one gap players game. I think he will bounce back and have a solid year next season on the end.
Traylor can play. He isn't just some 'fat guy'. You need great balance and need to have great hands to play on the nose. I've seen smaller guys do well and larger guys do well, and pure size doesn't have that much to do with being a good player. There are tons of 350 pounders out there but most of them can't play.