Common Spots: SB vs BB

The most common spot in poker with the widest ranges. What can GTO Wizard about this very important situation in poker?

Last week I started a 'study as I study' type series where I attempt to learn more about the most common frequency spots in poker. Inspired by this Tombos21 video, I first looked at BTN vs BB, single-raised pots. 

Today, I am going to look at a much more complex beast, 40BB SB vs BB, single-raised pots. This is the most common spot in poker and is very tricky to study because the ranges are so wide. Once again, we are using GTO Wizard to study this. 

First things first, let's compare the preflop ranges:

The BB defending range is very similar to last week's. It is most hands with any kind of equity, but it is capped because the biggest hands like AA-TT and AJ+ are mostly raised. Curiously, in last week's example, all the pocket pairs are raised, but here a lot are flat called. I suspect this is because the BB has position against the SB. 

The SB opening range is more interesting. It is very wide, and most hands mix betting or limping some of the time. However, it is somewhat polarised. Most hands are in this range, but the hands which always raise are very strong (like AA) or bluffs (like 63s). I suspect this is designed to remove some of the positional advantages the BB has. 

My instincts before we look any further is that we will see mostly small betting from both players on most runouts, with some large bets thrown in on polarising flops - not much medium bet sizing.  The SB has range advantage, the BB has positional advantage, but both have very wide ranges, so it will often be a stalemate. 

Using the aggregated reports at GTO Wizard, these are the flops the SB c-bets out on the most:

Paired or trip boards, usually with an A involved. It's very hard to hit these boards, so the preflop raiser will usually have the advantage and may not need to improve their hand to be well ahead here. The SB leads out 58% of the time across all flops here.

We can see from the reports that the SB has a slight range advantage of 53.7% and, on average, makes 4.26BBs against the BB. The primary bet size is small on most flops, but there are also large bets because of the polarity of the SB ranges. 

Facing a small bet, these are the flops where the BB raises the most:

Low boards are the most favourable boards for the BB, just like we saw in BTN vs BB. They are much more likely to hit these boards and make a hand top pair or better. Unlike when we wrote about BTN vs BB these boards are not so wet that a straight is possible right away on them. It seems the value in raising here is more because the SB has a capped range (they don't have many low hands) rather than the BB has so many nutted hands. However, the SB should bet often on these boards when they have a strong hand, because they are less worried about straights/flushes/draws. 

When the SB checks instead of bets, these are the most favourable boards for the BB:

Once again, it is low connected boards, but this time, it is flops where flushes and straights are very possible. The BB is slightly more likely to have hit these flops than the preflop opener. The SB is less likely to lead these boards in the first place. 

These are the flops the SB is most likely to check/raise:

Once again, it is the paired boards. Clearly paired and trip boards are best for the SB because they have the stronger preflop range, and the BB is so wide they are unlikely to have improved. 

Finally, these are the flops that are most likely to go check/check:

Monotone flops with mostly high cards. This makes sense; both players have most of the suited cards in, but they also have such wide ranges that they will have missed most of the time. The SB is more likely to make top pair here, but they also have the nut flush/draw less often, both because they have a high proportion of Ax. So it becomes a stalemate. 

So what have we learned from this little walkthrough? The SB prefers paired or trip boards the BB won't hit often; the BB prefers low boards the SB won't hit that often. However, the ranges are so wide for both players that the incentives seem to be to play things cagey a lot of the time. 

I doubt I have even scratched the surface here, SB vs BB seems like the most complex spot in poker. Let me know what you think about my assumptions in the comments. Finally, an overview of the best Bitcoin Poker Sites, which are also suitable for US online poker players.

What is GTOWizard?

GTO Wizard is an advanced GTO trainer that shows you how to play against a perfect opponent. 

You can play full hands from preflop to river to learn anything and everything you need to know to make your game harder to exploit. 

The interface is designed with learning in mind, with custom filters to drill down on important information, dynamic training modes to fine-tune spots, and advanced AI to do your own solves. 

You can also upload your hand histories to get your own GTO score and discover where you need to improve. GTO Wizard also has some of the best free strategy content available anywhere in poker. 

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