I'd be worried when he 4 bets pre-flop. At these stakes 4 bets usually means KK or AA. When he bets out on turn I'm really worried. Hard for me to believe he is bluffing/semi-bluffing with AK of clubs or anything.

Me, I'd probably call the turn, since I have position on him on the river and won't miss a bet there if he checks. He played it like pocket aces, and thats what he ended up having.

__________________
I find your response in this thread shallow, and pedantic...