Marko would kill himself if Webber won a title. It must be hard for any driver to give their best and stay motivated in that kind of backing. I think that's the real reason behind his slump post crash with Vettel. Webber was on the verge of 3 wins on the trot, despite was Marko says about him only being good for 3 races per year. After that he knew his chances were over.
They keep him on a tight leash with a 1 year rolling deal which I bet pays well but keeps him in check. 2010 showed how close they can be, but then Marko took a pee on him from high above.