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BB Defence vs Button Open (6-Max)

Facing a 2.5bb button open in the big blind you defend about 55% of hands: 3-bet roughly 9% (99+, ATs+, A5s–A2s, KJs+, AJo+, KQo) and call the remaining ~46%. You are getting 3.5-to-1 on a call, which is why folding most hands here is a leak.

Chart

3-betCallMixedFold

The pot odds are what drive this. With 1bb already posted, calling a 2.5bb raise costs you 1.5bb to win a pot of about 5bb — you need roughly 22% equity to break even on the call alone, and almost any two cards have that much against a 51% opening range. That is why the big blind defends more than half of all hands against the button, wider than any other spot in poker.

The 3-betting range is deliberately polarised: premiums that want a big pot (99+, AK, AQ) and suited wheel aces (A5s–A2s) that block AA/AK and make the nut flush. The suited wheel aces are the part most players get wrong — they call with them instead. Calling wastes their blocker value; 3-betting turns them into the hands that let you bluff credibly on ace-high and low boards.

The one thing that ruins big-blind defence is calling wide and then giving up on every flop you miss. A 55% defending range only pays if you actually continue on flops with backdoor equity and float the button in position-reversed spots. If you fold 80% of flops, you should be defending far tighter.

FAQ

How often should the big blind defend against a button open?

About 55% of hands in 6-max against a standard 2.5bb open — roughly 9% as a 3-bet and 46% as a call. The reason is the price: you only need about 22% equity to call profitably because you already have 1bb in the pot.

Which hands should the big blind 3-bet against a button open?

A polarised range: value hands that want a big pot (99+, ATs+, KJs+, AJo+, KQo) plus the suited wheel aces A5s–A2s as bluffs. The wheel aces block AA, AK and AQ, make the nut flush, and give you a credible bluffing range on ace-high boards.

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