I don't really put those two fumbles on Marshawn at all. The first one was just a perfect/perfectly flukey play by the defender, who got a perfect, blind shot that hit the ball just right. The second one was just hat-on-ball, something we see all the time from every back and something that's pretty hard to guard against.
I do think they should "conserve" him through the season, though, because his style is so punishing. He's a poor man's Earl Campbell.
"I have a Super Bowl ring, and I would gladly show that to him. And if he doesn’t have time to come see it, tell him he can Google it." -- Doug Baldwin