Someone wrote earlier why doesn't he take the pot at the turn if he plans on taking this without a hand and I agree with that. I don't see why an underpair would wait until the extra scary river after you've repped AQ or KK-AA to take the pot down with a bluff.

Maybe at best he has A10 or AK and was making a bad draw and you're splitting the pot. But if it's an uknown, I give him credit for a being a shitty-passive type player with a weak Q or J holding.

In a blind war I'd be more inclined to agree with the river call but even then, I dunno. I'm still not seeing enough blind battles at 100NL to not give a thought that someone is capable of a bluff in those either.