Suh's wired that way, he's a businessman who also didn't live up to the fat contract he signed in Miami. So the Rams signing him was a bit of an act of desperation, where they hoped the tiger would change his stripes. That was a questionable signing from the beginning IMO.
Matthews is different. He's not the same guy he used to be, but he does love the game and plays all out snap to snap. Only way to keep a guy like him fresh is controlling his snaps, which is what the Rams will do.
Question with Matthews is whether they can keep him fresh and have him ready to rock come the playoffs. And I think they will do that, plus he's going to fit really well here with Wade, to the point where i expect him to have a bit of a rebound season.