Defending against a flop bet

In this lesson

• Defend wider against small c-bets and tighter against big ones.
• Continue with most pairs and every real draw; fold hands with no pair and no draw.
• Choose fold, call or raise by hand class.
• Check a call against both the price and the equity your hand will realise.
• Work out alpha and MDF for the bet you face: alpha, bet ÷ (pot + bet), is how often a pure bluff must work, and MDF, 1 − alpha, is how much of your range must continue.

Read first: Which hands bet and which check · Advice, not a lock: every lesson opens.

Concepts used: MDF and alpha, Pot odds, Equity and equity realisation

Alpha and MDF, where they decide

The button bets into your big blind. Two numbers frame the decision. Alpha, bet ÷ (pot + bet), is how often a pure bluff must work. MDF, 1 − alpha, is how much of your range must continue for that bluff to stop profiting.

• A bet of a third of the pot, 1 into 3: alpha 1 / 4 = 25%, MDF 75%. Your call is 1 to win 4: you need 1 / 5 = 20% equity.
• A bet of three quarters, 3 into 4: alpha 3 / 7, about 42.9%, MDF about 57.1%. Your call needs 3 / 10 = 30%.

So small bets ask you to continue with much more of your range, and give you a much better price to do it with.

Why the big blind folds more than that

In Rail's solves of the big blind against the button, the big blind folds more than minimum defence says, against small bets most of all. That is not a contradiction. Minimum defence is the point at which a bet with no equity stops profiting; a defender whose range holds many hands with almost no equity cannot reach it without calling with those hands, and calling with them loses more than the bluffs win.

It also explains the other side: because the big blind cannot defend enough, the button profits from betting a lot of hands. Treat minimum defence as a warning light, not a target. If you fold far more than it, ask whether your folds are hands that really had nothing.

What continues against a small bet

• Most pairs continue, mostly by calling; the weakest fold more on boards that favour the raiser, such as ace-high ones. The best top pairs, two pairs and sets often raise.
• Every real draw continues: flush draws and open-enders call or raise, gutshots mostly continue.
• Ace-high continues sometimes, more often with a backdoor draw or a gutshot.
• No pair, no draw: fold. Backdoor draws alone rarely carry a hand; they decide the close ones.

Against a big bet the same order holds with the line moved up: the weakest pairs and the weaker ace-highs drop out first.

Price and realisation

A call needs more than the bare price. Out of position you will not always see the river, and some of your equity is in hands that will fold to later bets. That is realisation: a hand with 20% equity against a third-pot bet is not automatically a call if it can rarely get to showdown.

The drills are dealt from Rail's flop library, combo for combo. Your own hands on flops the library did not solve are read from the nearest solved flop by hand category, and the analysis marks them as mapped.

Rules of thumb

• Work out alpha and MDF for the size you face: smaller bets demand wider defence.
• Against a small bet, continue with most pairs and every real draw.
• Fold no-pair hands without a draw; let backdoors decide only the close ones.
• Price is not enough out of position: count how much of your equity you will realise.

When they break

• Against players who bet only strong hands, fold far more than any defence guide.
• Against players who bet every flop, call wider with ace-high and pairs.

Example hands

Practice

The lesson is mastered when every exercise below that Rail can grade is passed. Missed items come back later as review cards.