[StellarWind]

Easy flop fold with bad relative position. The odds are that someone has made a better pair and even if they haven't they will draw out on you a very large part of the time. Hero's implied odds are a disaster because of his terrible position and because the underpair will lose bigger pots than it wins.

Just to test my intuition I simulated this with PokerStove.

PFR range: top 16%
Limper range: 11th percentile through 45th percentile (this excludes hands he would probably open-raise)

The PFR has 39% equity, the limper has 37%, and Hero has 24%. Ouch.

My line is betfold turn/checkfold river. When 44 is still the best hand the ace will feel to most opponents like the roof is caving in. Hands like QJ will probably fold. A gutshot might call but assuming you survive the 10-out river he will miss the river bluff more often than not. People figure that you are afraid of the ace but that you still plan to call the river with whatever pair you checkraised the flop with. It might occur to Villain to put you on a busted straight draw but that's not a reason to bluff as he usually wins by showing.