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Pre-flop Play: The Gap Concept and Sandwich Effect

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The Gap Concept is a very straightforward idea that was first put forth by respected poker author David Sklansky. In a nutshell, the Gap Concept states:

You need a stronger hand to call a raise then you do to make an opening raise.

If the Gap Concept sounds simple, that is because it is. But like many simple ideas, it often winds up being undervalued or glossed over due to the Concept's seemingly obvious nature. I believe the Gap Concept remains highly relevant and worthy of consideration by all poker players, especially those seeking to play a tight aggressive game. Many inexperienced players (and more than a few experienced ones) frequently violate the Gap Concept without clearly thought out reasons for doing so. Over time this winds up creating a number of leaks in their game.

By learning how to use the Gap Concept, you can avoid three problematic situations that are fairly common pre-flop:

1. Losing your first in vigorish - When you are the first to enter an unopened pot with a raise you give yourself two ways to win the hand. You may win by having your cards hold up as the best hand in a showdown, or you may get other (and possibly better) hands to fold in response to your show of strength. Once a pot has already been raised in front of you, you lose the opportunity of being the first aggressor. So the cards that would normally be correct for you to open raise with in your position in an unopened pot now may not be playable.

2. Domination - Most players that you come up against at the low and micro stakes may have positional awareness, and the holdings that they choose to raise with from earlier positions will be stronger than the holdings that they'd raise with from a later position. To illustrate how this relates to the Gap Concept lets use an example:

Say you are holding AJo in MP2 in a Full Ring NLHE game and no one has yet entered the pot; normally we would consider this a reasonable holding to make an open raise with. But if UTG had raised to 4x the big blind and if UTG is reasonably tight then you have to consider what his standards for raising from early position are before you call. Let us give him a standard range of 77-AA, AQ and AK. Now consider the equity AJo has against this range and you will either be coin-flipping or severely dominated, significantly diminishing your positional advantage. Another reason to not call with AJo here against an early position raiser is that when an Ace hits the flop we will hit an attractive-looking second-best hand, which will cost us a lot of chips.

3. Getting Sandwiched - The Sandwich Effect (also coined by David Sklansky) occurs when someone makes a raise in front of you, you decide to call the raise with a marginal holding, and then someone behind you re-raises (also commonly referred to as a squeeze). This is the point where you find yourself smack in the middle of the Sandwich Effect, caught directly between the aggression of 2 players representing strong hands, and it begins to dawn on you that you really wish that you had never decided to call that initial raise with your marginal holding in the first place. Do you fold now and lose the money you have already invested? Do you invest more money with a mediocre hand into a very questionable situation? There may not be a great solution to this question especially if one or more of these players have a wider range than they are representing (other than having folded initially).

Applying the Gap Concept Pre-Flop

By appreciating the problems that occur when you ignore the Gap Concept then you will be more likely to apply the Gap Concept successfully pre-flop. You successfully apply the Gap Concept by tightening up your starting hand requirements when facing aggression and giving consideration to the tendencies of players left to act.

Just how strong your hand needs to be will depend in part on the observations you have on the pre-flop raiser. Against a loose-aggressive player or maniac, the Gap Concept is not as relevant because they play more trash and their raise does not necessarily mean a lot of strength. But against a raise from a tight or unknown player, your hand should at the very least be stronger than the bottom range of what you'd open raise with if you were in the raiser's position. Against a raise and a re-raise in front of you, you should only play your premium hands.

A few last notes:

Having an understanding of the Gap Concept is why many experienced players council newer players to place less emphasis on the use of hand charts to make pre-flop decisions. The strength of your cards and table position are only a part of the decision making equation. The action in front of you (and potentially behind you) as well as the types of players making those actions is a big part of the decision making process that goes into whether or not you decide to play a particular hand.

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