By far, one of the most significant and most common preflop leaks is failing to defend the Big Blind appropriately wide when facing a single open raise.
A subset of this leak is the failure to understand how small changes in RFI sizing impact the correct BB defending strategy width.
Since this leak is so prevalent, there is an above-average chance that it affects your poker game.
Let’s take a look.
Detecting the Leak
The easiest way to detect systematic under-defending is by looking at our BB cold call frequency (typically available with poker tracking software).
Our BB cold call should ideally be somewhere in the mid-30’s.
Anything noticeably below this in Texas Hold’em indicates we are missing opportunities to defend as wide as we should from the big blind.
Example – BB vs BTN 2.5x Open
As an example, let’s consider theoretically correct defending frequencies when facing a 2.5bb BTN RFI.
- GTO Cold Call ~24%
- GTO 3bet ~14.5%
The edge of the calling range includes holdings like Q2s, J4s, 63s, T9o and A7o.
If we realise that we never defend any of these holdings against a BTN 2.5x open, we are likely under-defending.
The Impactful Impact of Sizing
Let’s alter the above scenario so that we are facing a BTN min open (2bb) instead of a 2.5bb open.
For most, this minor detail would only provoke a slight adjustment to their poker hand rankings defending strategy.
Here are the GTO BB defending frequencies adjusted for the change in BTN RFI Sizing.
- GTO Cold Call ~49.2%
- GTO 3bet ~10.4%
We are now defending just under 60% of our holdings, compared to 36.5% when facing a 2.5bb open.
So, we are roughly defending an additional 60% of holdings due to a 0.5bb decrease in BTN RFI sizing!
Now we must defend almost any two suited cards, along with off-suit holdings as weak as 97o and K5o.
We can hopefully see that it would be a huge mistake to only defend ‘slightly wider’ in response to the 0.5bb smaller RFI.
Although 0.5bb is large in the absolute sense, it represents a significant percentage of the overall pot and therefore has a considerable impact on correct defending poker GTO strategy.
Putting it Together
We have only considered a single important scenario (BB vs BTN RFI). Mistakes with BB defence often occur against all positions.
The only solution here is to systematically work through each scenario while considering theory-based ranges.
Breaking down defending strategies by sizing is also crucial, as we have demonstrated.
Pay careful attention to the following -
- BB vs SB (Players under-defend here in general)
- BB vs Early min raises (Players don’t expand enough against the smaller opens)
If you are currently under-defending from the BB, it can be a good idea to expand gradually.
You’ll need the time to adjust to playing a wider range of hands postflop. Ultimately, we should be looking to defend even wider than solver against most opponents, since they will be making postflop mistakes.
Take your time with this topic – for most players, it’s by far one of the most profitable adjustments they can make to their approach.
