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Back to Basics (Part 3): Semi-Bluffing in Position

This is part 3 in the Back to Basics series. In this series, we take basic concepts and look at them in a little more depth than beginners typically do. The idea here is to fill in some knowledge gaps and play better poker on a fundamental level. In this week’s installment, we’re going to look at the idea of semi-bluffing in position, particularly in heads-up situations. Like the other installments in this series, you’ll need to have completed the EV Calculations Tutorial series to learn the quick-and-easy method for calculating the expected value of plays if you want to get the most from this article.

A Basic Semi-Bluff Scenario

Let’s look at a very basic scenario. Suppose we have four clean outs to the nuts on the turn in a heads-up spot. The pot is $30 and we have $25 behind with our opponent covering us. We’re in position, and our opponent checks to us. We have the option to go all-in on a semi-bluff. If our opponent folds about 40 percent of the time, we want to know if semi-bluffing is a good idea. We can do a quick EV calculation to find the approximate EV of our semi-bluff. Here are the three possible outcomes:

  1. Our opponent folds (40 percent), we win the pot of $30.
  2. Our opponent calls (60 percent), we hit our draw (4/46), we win the $30 pot and the $25 call.
  3. Our opponent calls (60 percent), we miss our draw (42/46), we lose our $25 bet.

EV of semi-bluffing = (0.40)($30) + (0.60)(4/46)($30+$25) + (0.60)(42/46)(-$25)
EV of semi-bluffing = $12 + $2.87 – $13.70
EV of semi-bluffing = $1.17

As we can see, our semi-bluff is going to be slightly profitable. This is the critical point in our analysis because this is the point that most people stop evaluating their options. We absolutely must investigate the EV of checking here to decide if semi-bluffing is the correct option.

The EV of Checking

If we check, then we could either hit our draw or miss. If we hit our draw, then we’re going to stack our opponent some non-zero percentage of the time. For the sake of example, let’s say that we stack our opponent just five percent of the time. Then we have the following potential outcomes after checking:

  1. Miss our draw (42/46), no win or loss.
  2. Hit our draw (4/46), no extra money goes in (95 percent), win the pot of $30.
  3. Hit our draw (4/46), get stacks in (5 percent), win the pot of $30 and the $25 bet.

EV of checking = (42/46)($0) + (4/46)(0.95)($30) + (4/46)(0.05)($55)
EV of checking = $0 + $2.48 + $0.24
EV of checking = $2.72

What you can see here is that checking is significantly better than semi-bluffing, and that would still be the case even if we never stacked off whenever we hit on the river.

Some Factors That Change Your Evaluation

We used a very basic example to show the thought process and the process of analysis here between choosing to check or semi-bluff when we’re in position. However, there are some other factors that could come into play in live scenarios that are outside of the bounds of this basic example.

For one, we could have a lot more money behind. This creates possibilities for future betting that tend to favor the semi-bluffing scenario. The reason for this is that you’re much more likely to stack off when you hit if you’re the aggressor on the turn than if you check and it’s obvious that you hit something on the river. Along similar lines, being on the flop instead of the turn tends to favor aggression as well since it means there are more chances for betting. It also sets up opportunities for the “free card play” if you bet the flop and are called with your opponent checking to your on the turn. In short, you have the opportunity to check through the turn to “get two cards for the price of one.”

The Effects of Position

Another important lesson to pull from this example is the effects of position. It’s easier for you to open the betting with semi-bluffs with confidence when you’re in position because most opponents that you face at small stakes will lack balance in their checking ranges. You’re going to be up against weaker ranges as a result, and this means you’re going to get more folds.

If you’re out of position, the value of checking a hand that you could semi-bluff with is typically going to be lower as well because you have to deal with the opponent betting in response to your check. When you’re in position, you get to immediately see the next card with a check. When the value of checking goes down, the relative value of semi-bluffing goes up. While being out of position does give you the option for the check/raise semi-bluff, that’s not normally going to be enough to make up for this inherent positional disadvantage.

Your Homework

Your homework for this week is to work through the same example above with the assumption that you have 6 outs or 8 outs instead of four. Make observations about how the value of checking and semi-bluffing change, and make observations about how the relative value of these two options change. Semi-bluffing is clearly worse than checking with just four outs, but does that change with six or eight outs?

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