What Is Minimum Defense Frequency?
Minimum Defense Frequency (MDF) is the minimum % of your range you must defend (call or raise) to prevent opponent from profitably betting any two cards. Formula:
MDF = pot / (pot + bet)
| Villain Bet Size | MDF | GTO Actual Defense* |
|---|---|---|
| 33% pot | 75% | ~58% (equity realization) |
| 50% pot | 67% | ~50% |
| 75% pot | 57% | ~42% |
| 100% pot | 50% | ~35% |
*GTO defends less than raw MDF because some hands cannot realize equity — they fold even though MDF says defend. Equity realization matters.
Example: vs a 33% pot c-bet on Q♣7♢2♠, GTO defends ~58% — calling with any pair, gutshots, backdoor flushes + overcards, and even ace-high. Folding more lets villain profit by c-betting 100%.
How Board Texture Changes Defense
- Dry boards (K♣7♢2♠, Q♣7♢2♠): Few draws, so defending is straightforward — call with any pair or decent ace-high, fold pure air. GTO defends ~55% vs 33% bet.
- Wet boards (J♥T♥4♣, 9♥8♢6♠): Many draws — you defend wider because many hands have equity (gutshots, flush draws, straight draws). GTO defends ~62% vs 33% bet.
- Paired boards (8♣8♢3♠, K♣K♢7♠): Trips are rare, so top pair is strong. Defend tighter — many hands have little equity vs trips/pairs.
Our Replayer shows GTO defense frequencies per board texture — import a hand and see.
Hand-by-Hand: Call, Raise, or Fold?
Spot: BB vs BTN open, Q♥7♢2♠ flop, villain bets 33% pot. You hold:
| Your Hand | GTO Action | Why |
|---|---|---|
| A♠5♠ (backdoor flush + overcard) | Call 58% / Fold 30% / Raise 12% | 38% equity, realizes 85% when calling. Backdoor + overcard is enough vs small bet. |
| K♣J♢ (two overcards) | Call 45% / Fold 55% | 25% equity but 6 outs to top pair. Close — blocker effects matter. |
| 9♣8♣ (gutshot) | Call 70% / Raise 15% | Gutshot + backdoor — too much equity to fold vs small bet. |
| 6♣5♣ (no pair, no draw) | Fold 85% | ~12% equity, no backdoors. Pure air — fold and save money. |
| Q♣J♠ (top pair) | Call 80% / Raise 15% | Top pair is strong on dry board — call to keep bluffs in, raise sometimes for value. |
Rule of thumb: call any pair, any draw (gutshot+), and any backdoor flush + overcard vs a 33% c-bet. Fold only complete air.
When to Deviate from GTO
- Vs tight c-bettor (bets only 40% of flops): Fold more — their bet means strength. Exploit by over-folding.
- Vs loose c-bettor (bets 80%+): Defend wider — they bluff too much. Call lighter, raise more as bluff.
- Vs calling station who never folds turn: Do not bluff-raise — just call with equity and fold air.
But you need to KNOW GTO first to know you are deviating. Lab Leak Detector shows if you over-fold vs c-bets and by how much.
Beyond the Flop: Turn & River Defense
Flop defense is just the start. GTO defense continues on turn and river:
- Turn: After calling flop, GTO defends ~55% vs a turn barrel. Many players over-fold turn — especially vs large sizings. If you called flop with a draw and missed, you often still have enough equity (backdoors, overcards) to call one more street vs a small bet.
- River: GTO river defense is tightest — you need a real hand. But vs small block bets (33% pot), GTO still calls with top pair weak kicker and even second pair. Do not over-fold river vs small bets from aggressive opponents.
Lab Replayer shows GTO frequencies for every street — import a hand that went to turn/river and see where you deviated.
Drill It: 5 Spots to Practice
- BB vs BTN, Q72r, 33% c-bet — which hands call?
- BB vs UTG, K72r, 50% c-bet — tighter defense, fewer calls
- BTN vs BB, JTs flop, 33% c-bet — wet board, defend wider
- CO vs BTN, A72r, 75% c-bet — big bet, defend tighter (~42%)
- BB vs SB, 882r, 33% c-bet — paired board, top pair is strong
Practice these in Lab Drills — auto-generated from your leak profile with spaced repetition.
FAQ
What is MDF in poker?
Minimum Defense Frequency — the minimum % you must defend to prevent opponent from auto-profiting by betting any two cards. MDF = pot / (pot + bet). But GTO defends less than raw MDF due to equity realization.
Should I always defend at MDF?
No — MDF is a baseline. Vs weak opponents, deviate: fold more vs tight bettors, call more vs loose bettors. But know MDF first.
How do I know if I over-fold vs c-bets?
Check Leak Detector — it tracks "fold vs c-bet" and shows your frequency vs GTO + bb/100 cost. Or filter your tracker: "folded to flop c-bet" and compare to ~42% GTO fold rate vs 33% bet.
What hands should I never fold vs a small c-bet?
Any pair, any open-ended or gutshot straight draw, any flush draw, and any backdoor flush draw + overcard. These all have enough equity to call vs 33% pot.