The River Block Bet: Why Small Bets Can Be Your Biggest Edge
The river block bet is a solver-derived discovery that revolutionized poker strategy.
I will break down why that is and how it helps you make more money at the poker table. I will start with a hand example, then dive into the theory behind the strategy, and finally tie it together to find the optimal solution.
Let’s dive in!
Laying the Scenario: To Bet or Not to Bet?
Why Do We Bet?
Let’s start with the basic premise. Why do we even bet?
There are a few different ways to approach this, but for our purposes, we will focus on the two main reasons:
- We bet because we are likely to win the pot at showdown when called.
- We bet because we expect our opponent to fold more than he should, thus generating a profit with a hand that doesn’t win often enough at showdown.
This brings us to the next question:
Why Do We Bet Different Sizes?
Different bet sizes create different mathematical constraints.
Smaller bets require the opponent to defend with a larger part of his range to prevent bluffs from becoming profitable.
Conversely, bigger bets require the opponent to defend with a smaller part of his range to prevent bluffs from becoming profitable.
This is known as the minimum defense frequency (MDF) concept, and it is one of the pillars of poker strategy.
The formula is as follows:
MDF = 1 – (Bet / (Bet + Pot))
This means that if you face a 50% pot bet, your MDF is equal to 1 – (0.5 / (0.5 + 1)). This is equal to 0.67 or 67%, so you need to continue with 67% of your range to prevent the opponent from bluffing you profitably.
Beyond the bluffing implications, bet size affects how thin you can go for value as well. We know this intuitively: the smaller you bet, the weaker the hand that the opponent is willing to call with, and vice versa.
While intuition is not always correct, in this case, the mathematics of the game corroborate it.
This is how the minimum defense frequencies look against different bet sizes:
We can see here that the smaller the bet you encounter, the wider you have to defend to prevent the opponent from having a profitable bluff.
Pro Note: The MDF concept only applies when the opponent has enough low-equity hands in his range to be able to overbluff. There are a variety of situations where, even in theory, the opponent simply doesn’t have enough very weak hands to overbluff with.
In addition, sometimes his bluffs will have high EV in the checking line. In such cases, it is optimal to over-fold compared to MDF.
What is a Block Bet?
A block bet is a small bet, below 40% pot, usually placed by the out-of-position (OOP) player.
When used OOP, it’s a bet to extract value from the weaker portions of the opponent’s range, while losing less against the stronger parts of his range.
Another strategic benefit is that it prevents the in-position (IP) opponent from creating a polarized betting range that would put an otherwise decent hand into a pure bluff-catching scenario.
When utilized in position, it is used by medium hands that need the OOP opponent to dig deep to call with enough weaker hands.
Now, let’s shift our focus back to the scenario from the beginning of the article once more:
Intuitively, the hand feels best, but it feels wrong to bet a “normal” size, like 50-75%, because it should not get called by enough worse hands.
It also feels like a waste to let the opponent simply check back with hands such as KJ, JT, TT, A9s, K9s, T9s, 98s, 88, etc. while allowing him to decide which bet size to use with his top pairs and better (along with several bluffs), putting you in a tough spot.
This is why the solver calculated a block sizing as the optimal line to take:
Is This Exploitable?
It is completely normal to worry about getting exploited in this spot. It is quite transparent which hand class you are representing for value.
In theory, your block-betting range will have some strong hands placed in that range which disincentivize the opponent from value raising too thinly. That being said, since your opponent is not a solver and also doesn’t know your exact strategy, what will he do about it?
Not much. By betting here, you force him into an unfamiliar spot. This means that he most likely doesn’t have prior knowledge of how to play this spot in a balanced manner. As a result, he is likely to make one of two mistakes:
- He will either over-bluff, which increases the EV of block-betting as you get to extract even more from his weaker hands.
- He will under-bluff, which means that you get blown off of your equity (via folding against a worse hand) much less frequently.
As long as you can accurately predict which side of the spectrum he will fall, block-betting will prove to be far superior in EV compared to checking with your medium-to-strong hands.
Why This Line Prints
This line prints in two ways:
- It allows you to extract more value from your made hands by tapping into your opponents’ weaker hands.
- It allows you to bluff cheaply, as most players are unwilling to call light enough compared to theory.
While I did already explain how the made hands end up generating more EV, I will now explain why this line is great for bluffing too.
Going back to the MDF formula, we saw that a smaller bet requires the opponent to defend with a wider range of hands. These small bet sizes of 20-33% pot are insanely hard to defend against correctly. Even seasoned pros struggle to defend with the hands that theory would require them to defend with.
Below is the IP player’s GTO defense against a 25% block-bet in the scenario I showed you earlier:
We can see here that the IP player should be sometimes calling with hands such as 88, 76s, and even 66. These hands seem like snap folds when there are flushes, straights, and two-pairs possible and relatively few non-made hands.
Furthermore, players are constantly getting in this spot with an even weaker range of hands than the solver would (as it slowplays with straights, sets, and two-pairs some of the time on the turn), meaning that your opponents will have more of the hands that fold in this spot.
This deviation has two implications:
- You should value-bet thinner as your hands have more equity (due to your opponents being too greedy on the turn)
- You should bluff more as your opponent will greatly overfold
In this specific spot, you should start turning all your 3x, 44, 55, and 66 into a bluff using the 25% pot size, as you can see in this exploitative model I created below (the light orange is the 25% pot size bet):
Note on In-Position Block Bets
I didn’t cover IP block-bets as they are not commonly incentivized by the solver.
The reason for that is that usually when the solver is OOP, it will preemptively defend against thin value bets by checking with a lot of its nutted hands. It would then deny the equity of the potential block-bet for value type of hands by check-raising extremely large using a balanced range. This means that thin value bets in position usually do better by checking back to avoid losing the pot to a weaker hand.
Wrapping Up
I strongly suggest you start implementing these types of strategies into your game if you want to reach the next win-rate level.
That’s all for this article! I hope I opened your mind to new possibilities and that you will start executing these strategies in your very next session. As usual, if you have any questions please let me know in the comment section down below and I’ll do my best to reply.
Till next time, good luck, grinders!
To learn more about how to use sizing to your advantage, read: Beyond the Flop Overbet: Elite-Level Turn Play Explained.
