What is a blocker and how do use it?
A “blocker” is any card that reduces the chance that the opponent has a certain range. Blockers are essential in 3-bet pots, on boards with drawing hands, at push-fold stages of tournaments, and when trying to pull off a bluff. Blockers are mostly used in Omaha, but sometimes they can be good for Hold'em.
POST FLOP SITUATIONS
Let's start with some math. In Texas Hold'em, each player gets two cards. These two cards can make 1326 combinations, which fall into the below groups:
• 78 suited hands (for example, AKs). There are 4 possible combinations for each hand (AhKh, AcKc)
• 78 off suit hands (for example, AK). Each of these hands can make 12 different combinations.
• 13 pairs (for example, 22). Each pair makes 6 different combinations.
So what is the function of blockers? Off suit hands (for example) block in total 101 combinations of 1326. Suited ones block 101 combinations, and pairs - 91. This is a fairly big number of hands, but in reality rival's range is much more limited. For example, you block the K2o combination, but the probability a rival will have such a combination is very low as it will most likely be folded pre-flop. Usually, you can put your opponent on a certain range, and then expel the combinations you block.
As an example of how blockers are counted in practice let's consider one of the hands played by our MTT coach. That was a 3 bet pot, and he made 3bets. Thus, in course of flop betting a rival responded to cbet. After the turn came, a rival responded to the coach’s check by another bet. After another check on the river, he decided to go all in. So, if the rival had a flush, which cards it was made of? Judging by the course of the hand, that could only be AJ, moreover - J-clubs, but it’s unlikely that a passive opponent with a low win on showdown would have bet on the turn. Other hands, like a set of sevens, would reraise and put all-in. Blockers on the flush: A, K, Q are all on the board. In the end, he decided to call, and as you can see he was right.
In tournaments, players think about blockers only in the form of "live" cards. Players say that if someone had pushed 65s and got called, he would almost always have live cards. This means that if there are no blockers for your cards, then they are live cards. For example, if you push A2, then in case of a call, you have more chances to stay with only one live card, since higher aces are not folded. Therefore, it's sometimes better to push 76s than QJo or A2o, as you'll have two live cards more often. On the other hand, a rival will fold more, since the number of his strong hands will be reduced due to blockers. There will be situations when we'll have no live cards at all while a rival holds a higher pair.
Below we'll consider the number of combinations vs different ranges. Including how many combinations there are in the range in general and how many will remain if we have one of the following hands: Ako, QJo, A7o, 65s. Let's assume your rival folds to our 3-bet tight range (AK, JJ-AA). It makes up only 40 combinations that is 3% of all existing combinations. Yet, if he holds AKo he will play the stack only with 2% (27) of the possible combinations. In other words, we will get the fold 33% more often. In any case, if we go all-in with AK, the rival will be less satisfied with the showdown then we are. The question is how our blockers change when hands change.
Having QJo, we block only 6 combinations of the tight range. So, if we go all-in, the rival will call only in 2.6% of cases, but in case he does call, we'll stay underdogs. If we have a blocker for an ace, then we'll get called by the tight range in 2.5% of cases. Only in 0.5% of cases, we will have no live cards at all (if a rival has pocket aces).
Today very few people play with such a narrow range - the range of AQo+, AQs+, and TT+ look much more relevant. In this situation, the rival will play the stack in 4.7% of cases, while having, QJo, for example, reduces this range to 3.9%, and A7o - to 3.8%. As we can see, blockers have reduced the rival's range, which he could bet/call all-in with by one-sixth. Weak aces have almost the same strength as high broadways. The higher a broadway, the more it affects the rival's range and pushes.
Yet, the more loose push/call ranges, the less important the blockers. At a very loose push range, QJo blocks only 16% of the range. That is, the looser is a rival, the less are the chances high broadways will block his range.
USING BLOCKERS IN PRACTICE
As mentioned before, blockers are mainly used in Omaha. Yet, sometimes they can be good for Hold'em. Blockers are very important for push-fold, but their effect shouldn't be underestimated in other situations. Usually, you should consider them when bluffing. A classic example of using blockers for bluffing was the critical hand played between Harrison Gimbel and Tyler Reiman in the heads-up PCA 2010. At first glance, Gimbel's bluff could seem insane, but this is how blockers work in practice.
He had an ace of hearts on the board with three hearts and was sure his rival had no nuts-flush, which means there was fold equity. Thus, he used his blocker to the nuts to represent the nuts. Blockers are often used to sets as well. For example, with two pairs on the flop, we have a blocker to two of the three sets. So, the probability of having a set is reduced by more than two times! Therefore, your rival will rather have draws, top pairs or lower доперы and you can bet safely against him.
You should always keep in mind what combinations your rival can't have or the chances that he will have them are too low because of pocket cards you hold. Blockers are not as important here as in Omaha, but oftentimes they might be critical in border situations.