progressBB defense vs BTN open at 9 BB
8-max MTT · ante 12.5 % · Button opens, small blind folds · chip EV
How the BB defends at 9 BB
Facing a Button open to 2 BB (small blind folds) with 9 big blinds, the big blind folds only 28% of hands, calls 48%, 3-bets to 4 BB with 3.0% and goes all-in with 21%. The big blind already has one blind in the pot and closes the action, so it gets a good price.
Always all-in: AA, AKs, AKo, AQs, AQo, AJs, AJo, ATo, A9s, A9o, A8o, A7o, A6o, A5o, A4o, KK and 7 more.
Folded: Q6o, Q5o, Q4o, Q3o, Q2o, J3o, J2o, T4o, T3o, T2o, 72o.
Against other openers at 9 BB the big blind continues with: vs CO 69%, vs HJ 72%, vs LJ 70%, vs UTG+1 70%, vs UTG 70%. The defence does not simply grow with the position of the opener here; the exact chart for each opener matters.
Closest decisions (the book continues with them only part of the time): 52o 50%, 63o 52%, 74o 54%, 32o 54%, J8o 56%, 95o 42%, plus 30 more mixed hands. These are the hands worth drilling, because a small change in the opponents or the stack flips them.
What changes around 9 BB
The book continues with 72% of hands here, 73% at 8 BB and 72% at 10 BB. Going from 8 BB to 9 BB, no hand crosses the 50% line; only the frequencies shift. Some hands switch to an all-in: 99, 88.
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Numbers come from the progressGTO solution book (v14, chip EV, 8-max, ante 12.5 %): our own equilibrium computation with a modelled postflop. It is an approximation, not an exact solution, and it keeps improving. Hover or tap a hand to see its exact frequencies.
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