i think id have to call this and take a note with whatever he shows up with.
dunno if its the best play, but it seems really easy for this spot to come up more in the future, would be good to have some info. plus there's a decent chance he has A5s, 87s, random air.
as a side note, this would be a pretty baller play if he had aces, and got you to hero call.
if hero was bob safai, this would be a great bluff by villain. but against a competent player, this is a bad spot to bluff because anyone decent can tell that the board texture polarizes villain's range so much, especially with that river. villain probably doesn't bluff very often on this type of board.
its kind of like last night's PAD imo. if that was bob safai instead of hellmuth, dwan bets less on the river to get the call. the overbet would be the bluffing line against a first-level thinker like safai. but against hellmuth, at least a 2nd level thinker, that is a horrible board to try to run him off of a hand. the overbet in that type of spot against hellmuth seems like its for value all day. not exactly sure how this is relevant here but even though the lines are different, it still basically seems like the same type of spot.