Pay attention to the stacks

People generally acknowledge the crucial importance of keeping track of the chipstacks of their opponents during a tournament, particularly a no limit tournament.

However, it can be occasionally relevant even in a limit cash game.

Here is a very simple hand where I think I cost myself a big bet because I didn't pay attention to the chip stacks.

hand #1
9 seated live $20/$40 limit hold'em game.
- preflop: LAG open limps in EP+2, good player limps in MP, fold, solid player limps in MP+2, folded to SB who completes, I check in BB w 8s3s (5 players, 5 small bets)
- flop: 2c3d8h, SB checks, I check, LAG bets, good player calls, solid player folds, SB calls, I call. (4 players, 9 small bets)
- turn: 2c3d8h9d, SB checks, I check, LAG checks, good player bets, SB folds, I check raise, LAG folds, good player calls all in. (2 players, 8.5 big bets)
- river: 2c3d8h9d2s, I show, good player mucks.

On the turn, I should be almost 100% certain to have LAG drawing dead, and 95% certain that I am substantially ahead of good player (the only possible better hand that he could have based on the way the hand was played that beats me is 89)

LAG: Based on the way the hand was played, LAG either has 1 or 2 overcards. If he had any pair or any draw, he would have continued to bet the turn. Thus, I should have let him in on the turn for 1 big bet. (if the right card comes on the river I may even try to check raise him)

Good player is either substantially behind or way ahead. I think his range of hands is pocket pair smaller than 8, 2nd pair 8s with moderate kicker, top pair of 9s with moderate-good kicker, and flush draw with 2 overcards. I think the latter 2 are more likely because I expect him to raise with either of the first 2 on the flop. With the latter 2 possibilities he has 8 and 9 outs respectively. He probably won't pay off on the river if he misses a draw (although there is a slight possibility since some people have a tendency to make a crying call with the last of their chips especially with A high even if they usually play well), but most likely would pay off with a pair. I don't think he will bluff bet the river if he misses his draw, so I would have to bet the river headsup.

I believe the reasons why I should try to get LAG to overcall the turn are: the pot is only of moderate size, LAG is likely drawing dead, if good player outdraws me on the river it doesn't matter if the bet goes in on the turn or river (since I would have to call his bet on the river). Basically, I believe I am only risking a fraction of a big bet of EV from good player (if he misses a draw and folds) by calling the turn bet. I'm guessing LAG overcalls the turn bet at least 50% of the time, and he'll probably improve enough on the river ~15% of the time to put in at least 1 more big bet.

I very roughly estimate that I have faced this type of situation (i.e. a very short stacked opponent that influences how I might play a hand) about once every 1000 hands, so it matters little to make this mistake every single time. However, it would have been quite satisfying to win an extra big bet or 2 from making a good situational analysis.

I think in this case I had just been playing in automatic mode making the standard check raise on the turn from the blinds with either a set or 2 pair.