The Key To Bluffcatching On Straight Boards

February 17, 2015 By: KasinoKrime

Hey guys, It’s Ph33roX from

I’m really happy to present this article I’ve written for the readers of PLOQuickPro. In this article, we will look a river situation on a low 4-straight board. Before I go into more detailed explanations, let’s look at the hand history we’re about to analyze.



As you can already see, Hero decided to call villain’s river bet with a bluffcatcher. By doing this, hero is betting that villain is over-bluffing in this situation.

We will examine how villain’s preflop range for opening under the gun affects his river range distribution and the correct betting strategy for him. Then we will try to estimate if it’s easier for him to deviate from the correct betting strategy by overbluffing or by under-bluffing.

Now, let’s start with making some assumptions about the range that villain gets to the river with.

Since villain is a competent regular, we assign him a preflop raising range of 15% – a reasonable range to open under the gun. On the flop, we expect him to cbet a wide range, so we build a cbetting range of 82% consisting of a pair of kings or better, 5x, 3x, flushdraws, any gutter and any hand with a backdoor straight draw + a backdoor flushdraw. PJ Syntax K+,ss,5,3,A2+,As,((Q,J,T,A):(Q,J,T,A)):dd

We call his cbet and our opponent checks to us on the 4 of clubs turn. Since the turn is bad for villain’s range, and we know he’s a competent player, we assume he checks his entire range, including his nut straights. We decide to check back, and so villain gets to the river with his entire flop cbetting range. River brings a 4-straight and villain bets into us.

Here is the visual representation of the river situation:


Let’s start with using the PJ bluffcatching module to see if this is a spot where villain can easily be over-bluffing. But first, we have to make some assumptions:

1. We assume villain value bets any six high straight or better.
2. We assume he checks and tries to show down with KQ+, hoping to win at showdown against a busted flushdraw or worse Kx hands.
3. We assume that any hand weaker than KQ is considering a bluff due to low showdown value.

The bluffcatching module will now split villain’s range into those three categories. Here are the results from the module:


We can immediately see that villain has very few straights in his range and that the rest of his range is split pretty evenly between hands with showdown value and hands without showdown value.

Villain can bluff with only 12% of his air hands which equals a total of 5.26% of his river starting range. This is due to the small size of his value-betting range and the odds that he’s laying us on a call with his chosen bet-sizing.

We can assume that villain prefers to bluff when he has a blocker. The most valuable blocker on this board is probably a seven. 7x hands without a straight comprise 6.70% of villain’s starting range, which is slightly more combos than what he’s allowed to bluff with (5.26%). If he only bluffs with 7 blockers, he’ll be almost balanced but still slightly overbluffing. If he’s sometimes bluffing with hands without a 7 blocker, he will be way-overbluffing.

Now, what if villain was opening preflop with a wider range? Let’s assume that villain is an aggressive regular opening from the CO with a 40% range. We go with the same flop and turn assumptions and we get a significantly different result:


Villain has straights 25% of the time now, a 84% increase compared to the tight opening range. He can bluff with 25% of his air range for a total of 9.66% of his overall river range. This means that villain can fire with his air more than twice as often now. If he’s bluffing only with 7x blockers, he’ll be slightly under-bluffing now, as those comprise 7.28% of his total river range. In order to bluff sufficiently he will have to add some other blockers to his bluffing range.

Now, before we go into summarizing all this information, you probably want to know what villain had. Villain showed down a busted nut flush draw with no relevant blocker. Seeing this showdown, we learn that villain is probably way over-bluffing in this situation. While it’s tempting to bluff the river on a scary board when you have complete air, one should be aware of his range. If you find yourself in villain’s shoes, remember to show restraint if you’re facing a strong opponent. Sometimes you just have to check/fold with most of your range and apparently this is one of those spots.


On 4-straight boards, river bluffcathing has a ton to do with the ranks of the straight cards and the preflop range of our opponent. In this example, a tight opening range on a low straight board has to show a ton of restraint with regards to bluffing river. If your opponent is often tempted to bluff when he doesn’t have showdown value, executing this super-low bluffing frequency can be rather hard for him. That means you want to widen your calling range. If you find yourself in villain’s shoes, try moderating your bluffing frequencies by sticking to bluffing with blockers.

If you want to learn more about playing on 4-straight boards, check out this article I’ve written about bluffing on a 4-straight board in a 3bet pot:

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