[adanthar]

Just by calling, one would assume he'd have an above average hand (or at least something that'd beat you PF.) If he's betting at you, you are probably behind, but your draw might be good (would he bet an unpaired A [img]/images/graemlins/spade.gif[/img] when you could easily raise the pot?) Since you also have a pair I think I'd call a pot sized bet and reevaluate on the turn.

If he checks I'd lean towards checking behind as I am very screwed if he CR's...but on second thought, it depends on how he's been playing. If I thought I could make him fold, I'd bet 2/3 the pot or more and see what happened.