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cash game big blind defense strategy

Big Blind Defense Theory in Cash Games Explained

Suppose you just joined a tough $25/$50 cash game online with 8 strong players.

You buy-in for 100BBs and wait for the blinds to come around. The cards are dealt. UTG min-raises to 2BBs and it folds to you in the big blind. You look down at Q♣ Q♠.

What is the theoretically optimal play, here?

You’re probably thinking that this is a slam dunk 3-bet 100% of the time. After all, QQ is way ahead of the UTG player’s opening range, she opened for only 2BBs, and QQ is the third strongest starting hand in poker.

If that’s what you’re thinking, then you would be wrong, theoretically speaking.

This article deals with the nuances of game theory-based play generally, and exploitative defense of the big blind in particular.

Why the big blind is different from every other position

In the big blind, we already have 1BB ‘invested’ in the pot. We can think of this forced bet as giving us a 1BB discount to enter the pot, and it means our pot odds against a raise are better from the big blind than from any other position.

Additionally, we get the option to act last preflop. This is a significant positional advantage; we can close the action when facing a raise, and see the flop without fear that a player behind us will re-open the betting.

Facing an open-raise from the big blind

To know what hands to defend in the big blind requires an understanding of why we fold the hands we fold.

Suppose we’re in the big blind and the action has folded around to us after early position raised. We do not have to worry about other players.

If the opponent’s raise size is small enough, then every hand will have equity against their range greater than the price we pay to enter the pot. And the opener’s range is fixed—if we call too wide, they can’t go back in time to make their opening range tighter than it already is in order to exploit us.

So, how can our opponents exploit us if we never fold our big blind?

If we call too wide in the big blind, our opponent’s high c-bet frequency becomes even more effective.

And there is nothing we can do postflop to stop them, unless we get lucky and hit a miracle flop.

Let’s look at an ad hoc example to illustrate this point. (We’ll return to the Q♣Q♠ in a bit, I promise):

Example: 9-handed cash game. 100BB effective stacks. Hero is UTG, and raises to 2BB.

The action folds to the big blind, who says to you that she only needs 22.22% pot odds to call (she’s fond of talking about math), and that every hand has sufficient equity against your range. The big blind calls without looking at her cards, and then checks in the dark.

Villain can have any hand, so your range crushes her range.

Your range will retain the upper hand in equity on every flop, with low connected flops like 6-5-4r being the worst for you at only a 51.13% to 48.87% equity edge.

Flop (4.5BB): J 7♣ 5♣

This is a relatively good flop for the big blind—her range has gained some equity over yours. Here 29.65% of your range makes top pair better (J9+). Although the big blind has all of the top pairs, over pairs, two pairs, and sets, only 9.69% of her range consists of J9+.

Attempting to bluff-catch with such a weak range will lead Villain into trouble. Even if you bet 50% pot on all three streets, she will struggle to defend enough to prevent your bluffs from being profitable. This means a couple things:

  • You can value bet your top pairs across all three streets comfortably.
  • You can bet hands like TT–88 for two streets of value, and check back the river.

At this point, it’s crucial to notice that, with so many value hands in your range, you will struggle to find enough bluffs to remain balanced. In fact, you need to bet your entire range.

(To learn the basics of constructing balanced attacking and defending ranges, read this article.)

You don’t have sufficient bluffs in your range despite betting every hand, so your opponent must fold more than the minimum defense frequency (MDF) on the flop or make a -EV decision. This means that you win EV with every hand in your range because your opponent has over-folded. (How much EV you win from fold equity depends on how much she decides to over-fold.)

If she chooses to fold all hands with less than 40% equity against your unpaired hands, then she would fold around 50% of the time. This means that your betting EV is at least (4.5BB pot + 2.25BB bet)*50% – 2.25BB bet = 1.13BB before considering the equity of your hand.

And so, when the big blind made the decision to call the extra 1BB preflop without looking at her cards, you gained the opportunity to profit at least 1.13BB by c-betting every hand on the flop. And this is true for almost every flop, which proves that it is necessary to fold some hands from the big blind, despite having equity that’s greater than the pot odds.

This was just a quick example with some back-of-the-envelope calculations. If you want to explore other whacky and wonderful spots (or common and standard spots) more deeply, I suggest you watch Fried’s solver module in the Upswing Lab. Click here or below to learn more about the Lab.

Building a game theory-based continuing range

The point of the above example was to illustrate why we should sometimes fold in the big blind when facing an open-raise, and how to effectively exploit players who over-protect their big blind.

But the principal question remains: how often should we defend our big blind?

With just two players in the pot—us and the raiser—our big blind defense strategy depends on two factors:

  1. The strength of the opener’s range.
  2. The pot odds we are offered.

In order to make a profitable call, our calling EV needs to be at least slightly higher than zero.

For example, if UTG opens 2BBs and it folds to us in the big blind, we need to expect to win back at least 1BB of the 4.5BB pot after the flop. We cannot call with hands that don’t satisfy this EV calculation.

Considering how likely it is we will face a continuation bet on the flop, it is very important to understand how our hand hits flops.

To illustrate, consider a hand like A 2. This hand has almost 38% equity against the UTG opener’s range. However, despite having this much equity, we can’t profitably call the min-raise.

We can use software like Flopzilla to determine how well our hand hits flops (displayed under “Statistics” below).

Our hand will flop two pair or better 3.8% of the time, and top pair 14.5% of the time. We should be quite happy with these outcomes. With top pair (or better) and UTG c-betting his entire range, we can bluff-catch with this hand, winning back some EV from the 1BB we invested.

However, with top pair and no kicker we will often be indifferent facing a c-bet on the turn. Top pair and no kicker is also too weak to value bet on many rivers if our opponent checks back the turn.

The remaining 81.7% of the time we will have trouble continuing with the hand:

  • If we pair our 2, which will happen roughly 13.5% of the time, we will face a near zero EV decision when UTG c-bets her entire range, since we have a pure bluff-catcher.
  • Similarly, we won’t win much by bluff-catching when we flop a gutshot, which will happen 11.3% of the time.
  • The remainder of the time we will have just Ace-high, which we will have to fold since we lose to better Ace-high hands that are in UTG’s range and are bluffing us.

All things considered, we can profitably continue on the flop less than 20% of the time with a hand like A2o. And so having to pay 22.22% to see the flop is not a profitable play.

For comparison, let’s consider a more connected hand like 6♠ 3♠.

We can see that 6♠ 3♠ is struggling against UTG’s opening range in terms of equity. But this hand flops much better than A2o.

Our hand flops two pair or better 4.95% of the time. Also, we will flop an 8-out draw (OESD, FD, combo-draw) 16.2% of the time, with which we will have substantial equity going forward, and which make very strong value they hit. With such great implied odds, calling a flop bet with one of these draws is very profitable.

So, with 6♠ 3♠ we can profitably continue on the flop at least 21.15% of the time. Combined with implied odds from making very strong hands like straights and flushes, we see that calling the 22.22% preflop is profitable, even if our opponent c-bets his entire range.

With such a good price we can continue with many hands, but our continuing range should mostly consist of hands that can draw to very strong hands postflop. Suited hands flop a two card flush draw 10.9% of the time, which is 10.9% more we can continue after the flop if our opponent has a high c-betting frequency. Likewise, connected hands can flop open ended straight draws and a number of gutshots. A connected off suit hand, like 65o, flops an OESD 9.71% of the time.

We should also play hands that make strong top pairs, which we can value bet on the river if our opponent checks back the turn.

Now that we understand what hands perform well as a call from the big blind, we can think about how our strategy impacts the EV of all our hands.

We know that if we call too wide preflop, Villain will c-bet her entire range on almost any board. As a result, we can’t see the turn or river with many of the weaker hands in our range, and so those hands will struggle to retain their equity.

If we play tighter, our opponent will c-bet less aggressively, and so we will see be able to continue with more our range, on average. We realize more equity playing tighter, and this increases the EV of all our hands.

The optimal preflop strategy therefore exists somewhere between (i) playing too many hands and being denied equity by aggressive c-bets, and (ii) playing too few hands and surrendering too much equity preflop.

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Okay, let’s talk about that QQ

By now you’re probably thinking back to our Q♣ Q♠, and how all of what we’ve discussed impacts our 3-betting strategy.

Our preflop calling range will still be wide, despite the disadvantages we discussed, simply because we’re getting a good price on a call and we don’t have to win very often to play. As a result, our calling range will be at an equity disadvantage, and Villain will still c-bet aggressively.

With very strong hands like AA, KK and QQ, the EV of calling the open-raise and bluff-catching or value-betting postflop is very high. However, one of these hands is not like the others: AA can confidently 3-bet and get all-in for value, but KK and QQ will usually either lose, chop or be ~50% against a value 4-bet range.

So, against our opponent’s small raise the optimal play with QQ is to call most of the time.

Perhaps you’re now wondering, when is it not the optimal play?

Against later positions, the EV of calling the raise declines when compared to 3-betting. This is because we can face a 4-bet from later positions more comfortably. We will often be ahead of our opponents 4-betting range, and we can call the 4-bet with the intention of bluff-catching postflop. Additionally, our opponent’s range will contain more weak hands, which means they will have a narrower range advantage than they would have had from an earlier position.

Opponents from later positions will therefore have a less aggressive c-betting strategy against our big blind calling range. This makes bluff-catching with QQ less effective.

Facing a larger open will shrink our calling range, because many of our hands will not have enough implied odds to call. With a tighter calling range, our range will be at less of a disadvantage, and our opponent will c-bet less often. Once again, this reduces the calling EV with our stronger hands, and so we can profitably 3-bet them preflop.

So, somewhat counterintuitively, against larger open sizes from an UTG player we will 3-bet QQ more often, and less often against smaller sizes.

Editor’s note: Keep in mind this argument is a theoretical one. In practice, you should typically 3-bet preflop with such premium hands in order to extract value. The vast majority of opponents will not play aggressively enough postflop to make calling more profitable.

Exploitative play from the big blind

Since we now know how a game theory-based big blind continuation strategy is built, we can think about how to exploit our opponents.

If we know the open-raiser will not c-bet often, then we can call with many more hands. This is because they will realize more of their equity by seeing the turn and river more often.

We should also aggressively 3-bet our strong hands preflop against this type of opponent, because we won’t be able to win as much EV by bluff-catching the their c-bet. The opposite is true for players who c-bet too often: we should call more and 3-bet less with both our weak hands and our strong ones. If the player opens too wide, then we can continue wider as well. If the player is UTG, but we think he has opened a range as wide as they should in the HJ, then we should play against this player as if the HJ had opened. The opposite is true if we think the player is raising too tight.

Cash game big blind defense conclusion

We’ve covered a lot of ground in this article, so here are the main takeaways:

  • Against players who call too wide in the big blind, we should c-bet aggressively as the open raiser.
  • When building our continuing ranges in the big blind, it’s more important to consider how well our hands hit flops than their direct equity against our opponent’s range.
  • Against smaller open raise sizes, we should call more and 3-bet less in the big blind.
  • Against players who do not c-bet enough, we should call and raise more when folded to in the big blind.
  • Against a player who opens too wide, we should defend wider in the big blind.

I’m confident you’ll be more profitable from the big blind if you build your strategy on these principles.

As always, post any questions and/or comments you have below, and good luck!

(Note: When it comes to studying poker, it can be tough to know where to begin. Study the game with step by step instructions and examples for a huge number of topics when you join the Upswing Lab. Learn more now!)

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Thomas Pinnock is a math whiz and Upswing member turned GTO wizard. When not preparing for his MD exams, he’s either playing poker, crunching numbers in the lab, or coaching. Get in touch on Facebook.

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