Haven't really seen the HW Overeem on his back yet. With more victories via SUB than KO, he's nothing to be messed with.
Damn EA MMA and spamming me with that stat constantly lol.
I might look back at a few of his fights though to see if he is good off his back. Maybe his subs were top ones? If Bigfoot can drag him down, and is Overeem looks a little big out of the water on his back, Bigfoot actually has an area where he can win the fight, especially since he's got great BJJ himself. All in all though, I see it finishing almost exactly how Lesnar got stopped.