20BB防守（20bb Defense）

Overview

20BB defense refers to the strategy adopted by a player in the big blind (or other defensive position) when facing an opponent's open raise (usually from the small blind or button) while holding a short stack of around 20 big blinds. At this stack depth, postflop maneuverability is limited, so the defender must adjust their range and play to avoid marginal situations.

Core Adjustments

• Reduce 3-bet frequency: At 20BB depth, a 3-bet often commits the stack, so 3-bets should be reduced and calls favored. The 3-betting range is typically polarized, consisting only of value hands (e.g., KK+) and a few bluffs (e.g., A2s-A5s).
• Widen calling range: The defender can call with a wider range, including many suited connectors, small pairs, and high cards. For example, facing a 3BB open, the big blind can defend about 50%-70% of down cards, depending on the opponent's raise frequency.
• Use squeeze plays cautiously: If the pot involves multiple opponents, squeezes may be reduced because postflop play often leads to all-ins and high variance.
• Simplify postflop decisions: After the flop, most situations should consider either going all-in or folding, avoiding complex betting. A binary "all-in or fold" strategy is common unless holding nut potential or a clear read on the opponent.

Example Range (Typical Scenario)

Assume the opponent opens to 3BB from the button, and the big blind has 20BB, no antes:

• Calling range: 22-JJ, A2s-AQs, A8o-AQo, K9s-KQs, KTo-KQo, Q9s-QJs, JTs, T9s, 98s, 87s, 76s.
• Value 3-bet/All-in: AA, KK, QQ, AK (sometimes called).
• Bluff 3-bet: A2s-A5s (blocker effect).

Notes

• If the blind structure includes antes, the defense range should be widened further due to better pot odds.
• Opponent's raise size and frequency affect the specific range; e.g., defend wider against a tiny raise (2BB) and tighter against a large raise (4BB).
• In tournaments, adjust according to ICM pressure, especially near the money bubble where a more conservative approach is preferred.