Big Pot River Decision

[Kevin J]

20-40

CO opens, button 3-bets, and I take a flyer from the bb with 22. CO caps it and both the button and I call.

*CO is a good, solid, thinking player who is capable of anything, but normally isn't too tricky. Button tries to play well, but just isn't there yet.

Flop comes 532 with two diamonds. I check, CO bets, button raises, I call, CO calls.

*Normally, I'd never slowplay here, but I wanted it to look like I'm on diamonds. I know button has an overpair, and wanted to find if CO had one too. Either way, I'm sure the turn is getting bet.

Turn is the Kd. Since, I played it like I had diamonds and there's no way I'm chancing it getting checked around, I bet. CO raises, button cold-calls, I 3-bet, CO 4-bets, button folds, I call.

River is a 4h. I check, CO bets. I....?