GTO Gecko
You just made a hero call to bust a 20-year old kid right on the tournament bubble, and now he's going off on you, saying you had no blockers to his value range. You're sitting there wondering what on earth he's on about. In this article, we'll cover the basics of blockers and unblockers and when they apply to your poker game.
Understanding Blockers
Having a blocker is the effect of having a specific card, which removes your opponent's ability to have that same card. This in turn has the effect of blocking multiple hand combinations in your opponent's range.
This means that:
- When bluffing, we want to block cards that are present in our opponent's calling range.
- When value betting, we want to block cards that are present in our opponent's folding range.
- When facing a bet while holding a bluff catcher, we want to block cards that are present in our opponent's value range, making it more likely they have a bluff.
Blocker Example: Single Raised Pot with Flush Draw
Let's say we're playing a single raised pot in a tournament on the button versus the big blind. The flop is Q♥ 7♦ 5♦, the big blind checks, we bet 33% pot and they call. The turn is 2♣, the big blind checks and we bet 110% pot, they call. The river is J♦, completing a possible flush.
When deciding whether to bluff on the river, our main focus should be on blocking our opponent's most obvious calls - in this case, a flush. A great bluffing hand with excellent blocker properties would be something like A♦4♠, as the A♦ blocks our opponent from having the nut flush.
Blocker Example: From the Defender's Perspective
Using the same scenario but from the big blind's perspective, when facing an all-in on the river, we need to evaluate what hands to bluff-catch with. An example of a great bluff catcher would be Q♣6♦. The Q♣ blocks our opponent from having value hands such as top set and top two pair, while the 6♦ blocks them from having rivered a flush.
A perfect example of how blockers matter more than absolute hand strength on the river is where 5♣4♦ would be a great +EV call (blocking flushes), while a much stronger hand in absolute terms like Q♠T♠ would be a significant -EV play to call.
Understanding Unblockers
An unblocker is the reverse effect of having a blocker. By having a certain card, you make it more likely that your opponent has specific cards. This has the effect of unblocking multiple hand combinations in your opponent's range, making it more likely they have combinations you prefer them to have.
This means that:
- When bluffing, we want to unblock cards that are present in our opponent's folding range.
- When value betting, we want to unblock cards that are present in our opponent's calling range.
- When facing a bet while holding a bluff catcher, we want to unblock cards that are present in our opponent's bluffing range, making it more likely they have a bluff.
Unblocker Example: Value Betting
Consider a single raised pot as the big blind versus the button, 50bb deep. The board is Q♥ 7♦ 5♦, we check and the button bets 33% pot, we call. The turn is 2♣, we check and the button checks back. The river is T♥.
When value betting, we want to unblock our opponent's calls, as we want to make it as likely as possible that they call our bet. In GTO solutions, a hand such as A♠7♠ is almost never betting, while 7♥3♥ on the other hand is always betting.
This is the effect of unblockers in the value betting context. When we bet a small size for value in this situation with only a pair of 7s, our opponent will have to call with a bunch of ace-high hands. When we don't hold an ace (like with 7♥3♥), it's much more likely that our opponent holds an ace, meaning they will call more often compared to when we bet with A7s.
So A7s blocks calls and unblocks folds, whereas 73s blocks folds and unblocks calls in our opponent's range.
Unblocker Example: Bluffing
Using the same board scenario, when bluffing, we want to unblock our opponent's folding range, making it more likely they fold to our bet.
In this situation, a great hand to bluff with is a missed flush draw because of the unblocker properties. When the button bets the flop and decides to check back the turn, they are much more likely to have a hand like J♥9♥ compared to J♦9♦.
This is because if the button has a flush draw themselves, they will simply bet the turn. When the button checks back, they are more likely to have a hand that had a backdoor flush draw on the flop (such as J♥9♥) that then decided to check back the turn when it didn't improve.
This means that a hand like J♥9♥, which will fold to our bluff, is much more likely to be in villain's range compared to J♦9♦. Thus, when we bluff, we would rather have J♦9♦ in this situation.
When Do Blockers and Unblockers Matter Most?
Blockers and unblockers always have an impact on a GTO strategy, from preflop all the way to the river. However, they matter the most when ranges get narrow. Blocking or unblocking specific cards in a tight range spot means that the percentage effect of having or not having certain cards will be larger.
Key Takeaways for Using Blockers and Unblockers
- For bluffing: Block your opponent's calling range and unblock their folding range
- For value betting: Block your opponent's folding range and unblock their calling range
- For bluff catching: Block your opponent's value range and unblock their bluffing range
Conclusion
Blockers and unblockers can be confusing at first, but they become easier to understand with practice. Use the GTO Gecko app to study different spots, just like in the examples we've covered. Look at which hands the solver chooses to bluff or value bet with, and try to understand the reasoning based on the blocker and unblocker properties discussed.
Understanding and applying these concepts can give you a significant edge in your decision-making process, especially in close spots where traditional hand strength hierarchy might lead you astray.
