How will J.J. Watt work in the Texans 3-4 defense?

Being a Texans fan that I am, I was hoping they would trade up for Patrick Peterson. Which didn't happen, then they had a chance to draft Nick Fairley and Prince Amukamara at the number 11 spot. But they decided to go with J.J. Watt, which frustrated and confused me, and probably a lot of other fans of Houston. That's where I get to this... How can a 6' 6, 290 pound defensive end fit in a 3-4 scheme? Definitely when the Texans already have a 6' 6 295 beast of another defensive end with Mario Williams. It just doesn't make sense to me how Wade Phillips can convert two huge ends and possibly have them play outside linebacker when they aren't built for it. I still don't understand this pick, Nick Fairley would have worked perfectly for Wade Phillips defense, since we don't have a dominating defensive tackle. This pick really disappointed me, unless their is a free agency this offseason, it's going to be another long season for the Texans D'...