Wednesday, April 16, 2008

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How to Put Your Opponent on a Range

David Sklansky: renowned poker theorist; cat owner.

By Daniel Skolovy

In his book The Theory of Poker, David Sklansky states that to play a hand correctly means to play it the exact same way you would if you knew your opponent's hole cards.

Of course, unless your opponent is especially clueless, this is never going to be possible in the real world. You should, however, be constantly trying to put your opponent on a hand - or, more accurately, a range of hands.

Oftentimes you will be playing and will hear someone say "I put you on x, so I called" or "I put you on y, so I raised." This is the wrong way to think about your opponent's holdings.

You'll rarely - if ever - be able to determine your opponent's hand down to the very two cards he holds. Instead, what you should be trying to do is assign a range.

Assigning your opponent a range is not as easy as it might sound. At the beginning of the hand you have little information, and thus his hand range is wide.

As the hand plays out you garner more information; thus, you can define his range more accurately. Let's look at an example:

Six-max game online. Effective stacks $200; blinds $1/$2. Your opponent on the button plays your average TAG game; let's say 18% of hands played, 15% raising pre-flop.

Pre-flop Action

The wrong way to think: "I put you on <em>x </em>hand<em>." </em>The wrong way to suntan: Whatever Eli Elezra did.

You have J-J and raise to $7 from under the gun. Two players call and your villain on the button calls as well.

Because of the limpers his calling range is very large - much larger than normal. Let's just take a couple minutes and fully think about it.

We can exclude AA, KK, QQ and A-K because those hands are almost always re-raised pre-flop. They are especially unlikely since your average TAG will not want to play any of those multi-way.

So if you were that TAG on the button, which hands would you call with? Well, hands that play well multi-way. When assigning a range it's never going to be completely accurate, but we can come up with approximations.

At this stage of the hand we can approximate his range as being:

• A-J
• Axs
• K-Qs
• K-Qo
• K-Js
• Q-Js to 5-6s
• J-9s to 9-7s
• TT-22

Granted, some of those are more likely than others, but that's the general range we can assign to his pre-flop call.

As you can see, it's huge. So far all you have to go on is his pre-flop call after two limpers. You'll have to wait until the flop to further define his range.

On the Flop

The flop comes 6-7-2. You bet $25 and the first two limpers fold; the button smooth-calls.

Your opponent called your raise after limping on the button and has now called your flop. You can take a huge number of hands out of his range.

First, you can eliminate the overcards. Our TAG opponent would fold the flop after missing. Chances are if he had 8-8 or 7-7 or some other overpair to the board, he would have raised the flop, so you can also discount those.

What we're left with is draws, sets, two-pair hands and weak one-pair hands.

After the flop his range looks like this:

• K-Qs to 8-9s in spades (although overcards, flush draws and open-ended straight flush draws are discounted, because most TAGs will raise the flop with those)
• 6-7s
• 8-9
• 7-8
• 7-9
• 7-7
• 6-6
• 5-5
• 2-2

All of these hands would at least call the flop. Some of them of course would raise but when assigning ranges it's sometimes helpful to use all hands that will continue to this flop bet.

As you can see, you've eliminated the bulk of his range. You're now left with a fairly good idea of what your opponent holds.

The Turn

The turn brings the T. You bet $50 and your opponent raises all-in. Do you call?

Let's look at his range, which you can define further. Which hands call before the flop, smooth-call the flop, and now raise the turn?

Like magic, the fog clears with more information.

His range looks like this. (Again, some of these are discounted because he would have raised the flop and not waited till the turn when a flush card came to make a move.)

• K-Qs to 7-8s (suited in spades)
• 8-9
• 6-7
• 7-7
• 6-6
• 2-2

His range obviously has you crushed. Very rarely would he take this line with a hand worse than this range. If you can't beat the bulk of his range then typically you should fold.

The Fog Clears With Information

What starts out as a hazy vision in the fog eventually becomes clearer the more information you get until you can make an educated guess as to his likely holdings.

Remember the idea is to not put him on one exact hand so much as it is eliminating what he doesn't have and coming up with a range of hands he likely holds.

Range is the greatest tool you can use to improve your poker game. If you can accurately deduce your opponent's range, you're going to be making fewer mistakes. And as we know, fewer mistakes equals more bucks.

More strategy articles from Dan Skolovy:

• Sit-and-Go Essentials Part 1: Low-Blind Play
• Sit-and-Go Essentials Part 2: Mid-Blind Play
• Sit-and-Go Essentials Part 3: Short-Handed
• Sit-and-Go Essentials Part 4: Heads-Up