I’ve been digging deep into SRP spots where BTN cbets and BB check-raises, especially on low flops (e.g. 742r, 963r). This is one of the most misunderstood lines in the game, and according to my research, one where most players, even solid regs, lose EV by folding too much.
The Default Advice is Wrong: Most people think “If BB check-raises and keeps barreling, they’re probably under-bluffing. Just fold.”
And at first glance, it makes sense. The XR-B-B line looks scary: usually all the chips go in by the river. Most regs assume this is always under-bluffed. But when you actually look at the mass data (MDA), you'll see that low boards are over-bluffed, even by your average passive reg.
It makes sense from a solver perspective as well. On low boards, BB has many draws and overcards. These make for intuitive check-raises, but actually XR at a low frequency. Here, I've highlighted BB's bluffs on 8♥ 6♦ 5♦:
BB's bluffs are highlighted. They're not allowed to raise their draws very often. Data shows regs XR around 3-4% too often on low boards like this one, and their XR range is too weak.
And most regs over-bluff on the turn and on the river as well. Again, the story becomes much clearer when you see just how little they're allowed to bluff on each street. For example, here's solver's river bluffing strategy:
BB is only allowed to bluff ~30% of the time on this river, making it very easy for some players to over-bluff.
When players over-bluff on prior streets, even just a little bit, they'll be massive unbalanced on the river due to the compounding nature of the mistake. The XR-B-B is a very low frequency line, so even small mess-ups on each street have massive consequences for bluff-catching.
That's why even your average, passive reg over-bluffs here!
The Exploit: Don't be afraid to bluff-catch on low boards. If you have a weak pair: you can often call. In one node-locked example, a weak pair (A5 on the board above) gained 17bb in EV. That's huge for a hand most players throw away!
But: Don't call with weak hands on the flop. Data shows most regs over-barrel on the turn in XR-B, so anything that can't call against a turn bet should be thrown out on the flop.
What do you think? Does this line up with how you play, or what you see in-game? Esp. interested in what live players think!
TL;DR: Most regs over-fold against flop check-raises and barrels on low boards in SRPs. Fear is costing them money. On low boards, even the average passive reg over-barrels according to mass data because it's so easy to mess up the right bluffing frequency as BB.