If Hendricks fails to dethrone GSP (I think Hendricks will knock him out though), I think the last challenge left is Lawler, assuming he can beat Rory. Lawler has the power and the striking to knock GSP out standing, and he's too strong to hold down at 170. If Koscheck had trouble controlling Lawler on the ground, GSP will too.
"Do you believe you're still as fast as you were, even 10 years ago?" -Michael "The Voice" Schiavello
"Maybe faster..." Steven Seagal