I hear they really like Charcandrick West and that he's the starter the rest of the year, Knile is the change of pace. I'm not sure they'll want Mason, he's not much of an upgrade.
Honestly though, I wouldn't be too opposed to trading Mason at the right price. It has to be a good deal for us though, because if Gurley goes down, we need a capable starter. I'm not sure Cunningham is an every down back, even though he's been awesome this year in his role. Watts hasn't played heavily against starting NFL defenses, could he do it? He looked amazing, but against backups. Malcolm Brown as well.
I'd need to get a fairly high pick back, like the 3rd we spent on him. I doubt you'd get that for him though, so it's probably not worth it. I'd rather have him for his occasional change of pace and spot start duties on his cheap contract. He's great insurance.