Walker, 25, was with the Falcons last season and was actually a pretty solid player for them. He’s much better run defender than an interior pass-rusher.
The Raiders have already lost Desmond Bryant to the Browns and it’s unlikely that Richard Seymour will be re-signed. Add in fact that Tommie Kelly could be released in the coming weeks, and it’s pretty clear that they need to add some defensive lineman to their roster. For what it’s worth, I see this as a pretty good move for the Raiders as they got a young player with a decent amount of upside.