Do you like this call or not?

Here's the situation, in broad outlines. I'm on the button in 6max and raise 3xBB with A8. One caller from the big blind.

The flop is 554. He checks, I make a standard continuation bet, he calls.

The turn is a jack. He checks, I check behind.

The river is an 8 giving me second pair plus the 5s. He bets the pot, I call.

Do you like this call, or not? My logic was this: with my pretty standard line (raise pre-flop, continuation bet, then a check showing weakness on the turn) he knows (or thinks) that he can steal the pot from me with a forceful bet on the end. He also may think that I think he is slowplaying the trip 5s, although I do not in fact think this. The particular size of the bet on the end - pot-sized - led me to believe he did not have a 5, and his check on the turn led me to believe he did not have a jack, either.

So that was my thinking, and why I called. What do you think? I will tell you the outcome in a bit.

If it were me I would think 1) he was slow-playing the 5. 2) He took a chance playing 76s for a 3xBB raise, or 3) He hit his 2pr with an 8 on the river just like you. I call to find out. Tough one tho.

Tough decision: Many players slowplaying the trips will make this play, so I would fold.

The outcome: he had garbage (Q9 I think) and was bluffing.

That looks like how I'd slowplay trips or I guess maybe a 4 of a kind...only hand that would come to mind to still play after a 3x BB raise.

Was the Q9 they even suited & the flop give him a flush draw?

I'd probably make the call just for information to get a read on the guy for later, especially with chips invested pre-flop and flop already and a semi-decent hand.