How Valuable Is Mario Williams To Houston's Defense?

This post is inspired by a discussion I heard on 790 while driving in to work this morning. The topic was Mario Williams--not whether he'd be back with the Texans, but how valuable he is to the Texans compared to his teammates. In other words, where does Mario rank in terms of importance and value against the rest of the roster?

In the interest of keeping the conversation as close to apples-to-apples as we can (knowing we're still sure to fail), let's narrow the scope of the debate even further. How valuable, compared to other Texans on that side of the ball, is Super Mario to what the Texans do on defense? Note that the question revolves around "value," not "potential" or "ability."

Which Houston defenders would you rank ahead of Mario in terms of importance to the success of what Houston does in Wade Phillips' defense?

Does that answer change if all of the players hypothetically made the same amount of money, so you'd purely be ranking Texans based on value without having to consider the difference in salary? For example, if all things financial were equal, does that push Mario Williams ahead of, say, J.J. Watt in your analysis? Or does your answer not change at all?

Enlighten the rest of the class with your answer in the Comments below.