I think Mike Swick is the most underated. I think it's coz of who he would have to fight to win the belt. His fight against David L. wasn't great but he won it.
It's possible we may see Swick v. Dewees for the belt, hear me out. We have seen Silva perform in the octagon like he runs the Matrix and that is what we will see against the TUF winner. We all know Dewees can bleed and evidently his body holds about 6 gallons of blood so WHEN Silva opens the first of many cuts there is a chance one might spray Silva in the eyes allowing Dewees to pull off the miracle.
It will probably be Swick v. Silva though.