How to exploit this common postflop leak
Imagine this scenario. MTT 20bb stacks and a BB ante. The BTN opens to 2bb, the SB folds and you call in the BB. The flop comes Jc 6d 5s and you check. How frequently should the BTN bet here? And what size (small or big) should he use?
The GTO solution has the BTN betting about 47% of the time (39% big bet and 9% small bet) and checking 53%. Does that surprise you?
The common mistake that many players make in this situation is to bet too frequently. In fact, a lot of players will just blindly bet this spot for a small sizing. So why do they do it and what can you do to exploit them?
Welcome to Exploit City
The clue to the first question comes from your response versus their continuation bet. They’re basically saying that they don’t believe you’re going to continue as frequently as GTO on this board and they’re also saying that they don’t think you’re going to check raise as aggressively as you should either.
When you face a 30% bet on this board, you should raise 20% of the time, call 51% and fold 29%. Your strategy looks like this:
How many players in the games you're playing are check raising here with Ks2s, Qc4c or Td7d? The answer, in low- and mid-stakes MTTs, is very few. Are you check raising with those hands? Heck, are you check raising most of your Jx, and just calling your two pairs?
Now, if you reduce this check raise frequency to get rid of those ‘unusual’ hands like Ks2s, Qc4c and Td7d, then the BTN/IP can now bet much more frequently for a small size, which means he checks back much less frequently. Incidentally, he should still use a big size a decent chunk of the time, as you can see below:
But it’s still not a range bet, is it?
Are they really range betting?
So here’s the thing. Many poker players incorrectly believe that they’re not making a huge mistake to bet small with their entire range on a number of different boards. To be fair, the EV difference on the flop probably isn’t that significant, but the problems arise when they try to construct their ranges as the hand progresses. They’ll land on turns and rivers with too many weak hands and will be up against a stronger range since they expect the BB to just roll over and either fold too much, not check raise aggressively enough or not play certain parts of their range in the right way, i.e. check raising two pair when calling is the highest EV line. So while betting small with your entire range isn't that much of a mistake and is certainly an easy strategy to implement, you open yourself up to misplaying turns and rivers and, most importantly, to a counter-strategy.
How to exploit the leak
If you run the same spot in PIOSolver and force an IP cbet, the OOP/BB response is now to check raise almost 41% of hands, call 36% and fold 23%. That’s a huge difference – check raising more than twice as aggressively.
Here’s what the two strategies look like – the BB response versus the GTO small size on the left, the BB response to a small sized range bet on the right:
At first glance, the most obvious changes come from what you should do with top pair, second pair, ‘nothing’ and gutshots. Let’s take a look at them in more detail.
Versus a range bet you should check raise your top pairs much more aggressively.
You should also play your second pairs more aggressively, too!
‘Nothing’ is categorised as those hands that are less than King high, but can include draws (see below). As you can see, there’s a lot more raising going on here as well.