Blockers & Unblockers: The Secret to Picking Great Bluffs

Blocker/unblocker was a concept my coach, Dara O’Kearney, showed me in relation to bluffs. It is one of those things that you cannot unsee once you have been shown it. It applies to pre- and postflop, and it really helps you identify good bluffs when you’re in the midst of a hand.

A good bluff should simultaneously block very strong hands and unblock the hands that we want to fold out. Blocker/unblocker is a useful heuristic for picking powerful bluffs. It is particularly pertinent preflop and on the river.

Preflop

Let’s jump right into a hand example to see what blocker/unblocker is.

Cash Game Hand Example

This is the NL500 opening range for UTG:

In response to the open, this is what the HJ strategy looks like at equilibrium:

It’s a pure raising range, of which about half the hands UTG opened.

We can answer that by looking at the UTG response to the HJ 3-bet:

A5s–A3s are clearly bluffs; they can make better hands fold like A9s–A6s and some small pocket pairs. KQo is also a bluff; similarly, it can get folds from some Ace-x and small pairs. However, these hands also make worse hands fold, but we are happy enough to take down the pot this way (especially to avoid paying rake postflop).

These might seem like quite strong hands to turn into bluffs. One of the reasons they are so effective is that:

They simultaneously block and unblock the right hands.

A5s, for example, blocks the really strong hands like AA and AK. It also unblocks a lot of weaker (but still threatening) hands that fold like K9s–K5s, QTs–Q8s, and so on. So, just to be crystal clear, the Ace is a blocker, and the 5 is an unblocker.

Tournament Hand Example

Let’s look at a spot where preflop action is more significant, and taking the pot down then and there is very valuable, i.e., in tournaments. These are 20bb symmetrical stacks near the bubble. This is the CO opening range:

This is how the BTN responds:

A lot of folding, not much calling, and an almost 50/50 mix of shoving and raising to 5bb (with slightly more shoving).

This is the CO response to the 5bb raise:

This is the CO response to the all-in (20bb) raise:

Looking at the folds, we can tell the primary bluffs are, once again, low suited Ace-x. They block the stronger Ace-x continues, while also unblocking all the suited Broadway hands that fold. There are some suited Broadway bluff-shoves like KQs–KTs. They block many of the calling hands, such as KK, QQ, AK, AQ, JJ, and TT, but also unblock folding hands like the small pocket pairs, as well as Ace-x. We also see a small amount of bluff-raising with hands like K3s, which block KK/AK calls and unblock a lot of the suited Q-x and J-x hands that fold.

Notice that we do not see bluffs with hands like J3s. And it so happens to be that they mostly go against the blocker/unblocker heuristic:

There is another reason why we mostly pick suited hands like A5s and K3s for our bluffs. They block strong hands, they unblock folds, and crucially, they can make very strong hands when called. A hand like A5s or K3s is in bad shape when it is called by AA, KK, or AK, but it still has a little bit of extra chance of outdrawing via a flush by the river. The low cards in the bluffs are also at least ‘live’ in the sense that they have some outdraw possibilities by making a low straight or trips, which the AA and KK-type hands cannot.

This is why A5–A2s make particularly strong bluffs. They block continues, they unblock ‘discontinues,’ they make (nut) flushes, and they make (wheel) straights.

Postflop

Let’s look at this concept in a postflop scenario. This hand is on the river of an NL500 cash game. UTG has opened, and the BB has called.

These are the ranges for both players on the river with their equities:

UTG has all the nutted (90%+ equity) hands, but the BB has a lot of strong (70–90% EQ) hands they will want to get value with by betting them, which means they will also need some bluffs.

With that in mind, this is the BB’s first action on the river:

Mostly checks, but ~5% of the time, the BB leads. They have straights, two pairs, and top pairs that all want to extract value and do not want UTG to check back.
That means they also need some bluffs. Given that ~48% of hands in the range are under 50% equity and 14% of the range is considered ‘trash,’ the BB has plenty of options for the bluffs.

Looking at the flop, my initial instinct regarding bluffs would be to prefer 8-x and 7-x because they block straights. I’d be avoiding bluffing spade or heart draws that missed, because I know that missed flush draws often make bad bluffs because they block other missed flush draws that would make up a big part of the folding range. I’d probably pick K8s, even though the only available combo is spades, because it blocks straights, AK, KK, and K9.

However, the actual commonly used bluff hands here are all suited misses! 8♠4♠ and 7♠3♠ are pure bluffs. 7♠4♠, J♠8♠, T♥8♥ and T♥7♥ are frequent bluffs.

The fact that they have the suits from the missed flush draws is probably because there were two flush draws by the turn, and any hand with diamonds or clubs will have gotten out of the way already. So, the heuristic of missed flush draws being bad bluffs is not disproven, but here, we don’t have many alternatives to choose from.

Every hand has an 8 or 7, which obviously blocks the straight. Let’s look at the response to the 35% pot river donk-bet to learn more about the unblocker properties of our bluffs:

UTG folds ~30% of the time. The hands that fold are predominantly Broadway hands that had a flush draw as well! Hands like K♠Q♠, K♠J♠, K♥J♥, K♠T♠, K♥T♥, K♠8♠, K♠7♠, Q♠J♠, Q♠T♠, Q♥T♥, JTs and some offsuit hands like KQo, KJo, KTo, QTo etc. There are other hands that fold, but most of the folds are unpaired hands with a King or Queen in them.

All of our primary bluffs unblock those hands. A hand like 8♠4♠ blocks the nut straight and also unblocks all of those Broadway folds. This is not a high-adrenaline bluff that would make a TV highlight reel by getting a monster to fold; it’s merely targeting all the trash in the range. Hands that would all check back if it was checked to them.

Looking back on what my instincts were, K8s would be a terrible bluff because it blocks half of the hands that would have folded.

A very useful postflop tool for studying this further is the value and trash removal scores in the “Summary” tab. When we bluff, we want to remove value, but not trash.

These are the scores for some of our bluffs:

Let’s compare that to K8s, which I thought would make for a good bluff before studying this spot:

It’s true that K8s removes more value, but it also removes much more trash, which we do not want because trash (better than our own trash) is all we can get to fold. So, in this hand example, our bluffs are primarily being selected based on their unblocking properties.

Going back to the UTG response to the lead, they raise the BB’s lead 30% of the time, mostly by going all-in. The value is mostly sets and two pairs, but what about the bluffs?

The most common bluff is 9-x: K9s, Q9s, J9s, and 89s all turn their second pair into a bluff. The other common bluffs are the small pocket pairs (44 and 33). Finally, K5s when it is not spades bluffs.

Let’s look at the BB’s response to the UTG river raise shove to see why these hands are picked to jam:

Most of the two pairs that call feature a 9, and a set of nines is in the opponent’s range, so the 9 blocks a lot of value. 89s is the master blocker in this respect, as not only does it block two pairs and sets, it also blocks the straight.

The BB did not bluff at the start of the river action with a K/Q/J because these cards were in the hands that UTG would’ve folded, so the BB picked hands like 84s, which unblocked those folds. This is precisely why these same high cards are in the UTG bluffing range; they were never in BB’s bluffing hands. So, these cards unblock BB’s bluffs.

What is a bad unblocker for one player is (often) a good unblocker for their opponent.

The other hand class that bluffs is the small pairs (44 and 33). They have the obvious blocker value of blocking the wheel straight. They also unblock the J8s–J7s, T8s–T7s hands that all bluffed. K5s also belongs to this category. Low pairs turned into bluffs are pretty similar. The difference is that they block another sort of value; instead of straights, they block some two pair combos that call. The similarity is that they also unblock the same bluffs as 44 and 33 do.

Another useful tool in GTO Wizard is the “Blockers” tab, which shows you whether a particular card in one player’s range increases or decreases the other player’s frequencies of folding/calling/raising. For example, these are the cards in UTG’s all-in raise range:

The 3♠ is the most powerful blocker, which is found sometimes in UTG’s bluffing range with 33, as it simultaneously blocks straights and unblocks the hands that fold. (The only fold with a 3 in it is 73s, which is a tiny part of the opponent’s range). It increases the chances of folding by 2.78%. As you can see, 6-x and 9-x also increase the folding frequency significantly, and UTG’s bluff range had a lot of 9-x in it.

Similarly, this tab can also reveal the cards with the worst blocker value for your objective:

2♠ is the worst card to bluff with, as it unblocks all the strong two pair combos that call, as well as blocking the only two pair combos that fold. Having this card in your hand increases the chances of being called by 5.93% at equilibrium.

My previously suggested K♠8♠ bluff really does look terrible based on the data in this table, as both those cards increase our chances of being called by a combined 0.5%.

Conclusion

I picked preflop and river examples to cover this heuristic because, in my experience, that is when the blocker/unblocker effect is most pronounced. On the flop and turn, improvability is perhaps a more significant factor when picking bluffs.

We saw that blocker/unblocker is a heuristic for picking bluffs. With two cards in your hand, it is possible to find bluffs where one of your cards blocks value and the other one unblocks folds. But this heuristic can guide us in the process of value-betting as well. A good hand to value-bet will unblock worse hands that you want to get called by while also blocking better hands that you do not want to get called by.