MDF: When Not To Use It

Minimum Defense Frequency is something I almost never use in my own calculations when making call/fold decisions, though it has become very central to a lot of modern poker theory.

I find that when framed from the perspective of the player betting the idea is fundamentally useful: if I bet with what I think is a bluff, how often does a better hand have to call before my bluff is not profitable? But when framed as a tool for making calling decisions, I think it is not what you should usually be leaning on.

So why is that? If MDF is something you should consider when making bluffs, why do I completely ignore it when deciding whether or not I should call?

Keep in mind my thoughts here are still a bit squishy, and certainly nothing definitive. I expect and welcome some disagreement on this point. That legal disclaimer out of the way…

I think MDF simply does not define the cards you can actually call with profitably. Especially if we are talking about river call/fold decisions, I really don’t care what the entirety of my range looks like. I don’t need to look at the size of the bet I’m facing, and if MDF is 75%, call with the best 75% of my range. I have a single hand, and it is my opponent that still has a nebulous probability distribution of a range.

  • Picture that range
  • How much of it are you ahead of, and how much are you behind?
  • What are your pot odds?

Do those three things, and I think you have something that will serve you much better when deciding whether to call or fold than MDF. If I think I’m ahead 35% of the time, then that’s enough to call a pot sized bet. If pot is $1, over 100 iterations, I’ll lose my $1 65 times, but pick up $2 35 times.

If you are not on the river, life gets still harder, and on any street, it’s never really only a call/fold decision, as you always have the option of raising also.

That said, I do think you benefit from understanding MDF, as it defines how often you need to call with a better hand to keep bluffs from being profitable, and helps you to see when you or others are essentially begging for bluffs.

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