[PShabi]

Okay, 99 on a 632 flop is an overpair, not middle pair.

When you check to him on the river, he's betting, not raising.

Now, the first thing I ask myself on every street of every hand is how big is the pot.

So, let's say you have 99 in MP here. You raised preflop, got 3-bet and called. 7 small bets if blinds fold out. You bet the flop, get raised, you reraise, he calls. 13 small bets. Take the rake and you conver it to 6 big bets.

Now on the turn 2 more BBs go in for 8BB. Ace hits on river, you check and he bets giving you 9 to 1 on the river.

Now, you only need to be "good" 1 out of 9 times to break even. I think in this situation you can expect to win a good deal more than 1 out of 9 times.

Call and if you lose, just know that the play will make you money over the long run.