Minimum Defense Frequency MDF

Concept

MDF (Minimum Defense Frequency) is a theoretical concept in Texas Hold'em used to measure the frequency with which a player must defend against a bet in order to remain unexploitable. It is based on Game Theory Optimal strategy (GTO), assuming the opponent's bet is either a pure bluff or a value bet, and the bet size is known.

Calculation

The formula for MDF is:

MDF = Pot Size / (Pot Size + Bet Size)

For example, if the pot is 100 and the opponent bets 50, then MDF = 100 / (100 + 50) = 66.7%. This means the player must continue with at least 66.7% of their hands, otherwise the opponent can profitably bet with any two cards.

Applications and Limitations

• Theoretical application: MDF is primarily used to construct a balanced defense range, preventing frequent bluffing. In GTO strategy, players should aim to approximate MDF, but in practice, opponent tendencies and range advantage must be considered.
• Adjustments in play: Against aggressive opponents, you may increase your defense frequency; against passive opponents, you may lower it. Additionally, MDF does not account for implied odds, range vs. range dynamics, etc., so it should not be applied mechanically.
• Common misconceptions: MDF is not equal to calling frequency, because raising also constitutes defense. Moreover, MDF applies only to heads-up, single-betting-round scenarios.

Example

Suppose on the flop the pot is 100, and the opponent bets 50. MDF is 66.7%. If your hand range contains 100 combinations, you should continue with at least 67 combinations (including calls and raises) to avoid being exploited by any two cards.

Summary

MDF is an important tool for understanding poker theory, helping players build unexploitable defensive strategies. However, in practice, it must be flexibly adjusted based on opponent type, board structure, and your own range.