Why Blocker Cards Matter
I get a lot a questions about blockers and how to use them. Blockers - or blocker cards - are an intermediate poker concept and can seem a little mysterious. However, there’s nothing particularly mystifying about them.
Simply put, a blocker is a card that decreases your opponent's chances of holding a particular hand through inhibiting (i.e. blocking) combinations of that hand by virtue of what's in your hand.
To truly understand blocker cards, we first have to understand a nifty little concept called combinatorics. It sounds more complicated than it actually is, don’t worry.
Blocker Cards and Combinatorics
It’s best (and easiest) to begin our talk about combinatorics by talking about their root word; namely, combination. When talking about poker, a combination refers to the cards that make a poker hand. In No-Limit Hold'em, a combo would be 2 cards (your first and second). We're talking unique cards, including not only the rank, but the suit as well. So in Omaha, for example, the combo would be 4 – but we won’t get in to Omaha right now, since as a game, it’s considerably more complex.
Moving on then. Next, we need to consider the composition of the combination.
How do combinations give us the composition of a hand?
Consider pocket aces. There are 6 possible combinations of this hand (A♥A♦, A♥A♣, A♦A♠, A♦A♣, A♠A♣, A♠A♥). As some of you know, the chances of winning this coveted combo are 220/1. That’s 2652 total hands in No-Limit Hold'em. Out of those 2652 hands, 6 of the possible hands are pocket aces. (You can also think of 1326 unique hands, since the 2652 double counts hands, treating A♠A♣ as different from A♣A♠, for example.)
Unpaired hands are significantly easier to make than paired hands. AK can be dealt 16 different ways because unlike AA, we have 2 sources to make 8 cards instead of 1 source of 4 cards. Using the same logic, when we have suited hands, we've got 4 combos.
Why are the odds of getting certain hands important?
Because playing winning poker is about hand reading and ranges. Combinatorics are the foundation of understanding and manipulating ranges.
Let's look at a quick example using the top 3% of hands, which are Jacks or better. The combinations of each hand determine the weighting of the range. This top 3% (AA, KK, QQ, AKs, AKo) has a total of 40 possible combos AA (6), KK (6) QQ (6), JJ (6), AKs (4) AKo (12). This gives you a composition of 60% big pairs, 40% Big Slick (includes suited and off-suited).
Now this is where blockers come into play and can change the fate of the game.
If you happen to be holding Q♦J♦ in your hand against an opponent who plays this top 3% hand, now he doesn't have big pair 60% of the time and Big Slick 40%; now he has AK 47% of the time, and big pairs 53% of the time. That's a significant change. And this is the power of a blocker. There are only 3 possible combos left; namely, Q♥Q♠, Q♥Q♣ and Q♣Q♠ and J♥J♠, J♥J♣, and J♣Q♠, since the diamonds are in our hands.
Remember: A blocker is a card that decreases your opponent's chances of holding a particular hand through inhibiting (i.e. blocking) combinations of that hand by virtue of what's in your hand.
If you hold the A♠ on a three spade board, even if an opponent makes a play at you, you know he can't have the Ace high flush because you have the blocker - the key card that would help him make that flush. Holding a blocker changes the weighting of your opponent's range, making certain hands more likely and others less likely. Using the last example, having the Q or the J decreases your opponent’s chance of having a pair, but it doesn't decrease his chance of having AK.
The Good News for the Not-So Numerically Inclined
Even if you're not a math person, having a general idea of the concept of blocker cards is enough to help you. A basic understanding of what you're holding, the board cards and your opponent's range will give a solid player a good feel for blockers.
Blockers can apply to pre and post-flop situations. In pre-flop play, a blocker decreases chance of your opponents having a premium hand because you can block them; likewise, in post-flop play, a blocker can make crippling monster hands like sets, flushes, straights and full houses less likely because you can prevent the hand from being made.
Now, if this concept is still a little hazy, I strongly recommend you get some visual assistance and check out my video tutorial on blocker cards. If you want some help with ranges, check out my hand range charts, which are available at the Gripsed store. These charts are particularly useful if you’re not much of a math person.