In chapter 5 of PLO From Scratch, Bugs develops a mathematically grounded framework for 4-betting and defending against 4-bets with 100BB stacks, showing that these situations are largely governed by pot odds, equity thresholds, and hand structure rather than guesswork.
Why 4-Bet Pots Are Technically Simple (but Crucial)
With pot-sized raises up to the 4-bet, stacks are structured so that:
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Only one pot-sized bet remains after the 4-bet.
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Postflop play usually reduces to a single all-in decision on the flop.
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Correct play can be analyzed using pot odds and flop equity distributions.
Because of this low SPR structure, many 4-bet scenarios are mathematically “cut-and-dried.” That makes them important and relatively easy to fix if leaks exist (for example, folding too often on flops in 4-bet pots).
Part I: 4-Betting
When Should You 4-Bet Light?
Bugs begins with a key contrast:
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Against a player who 3-bets only AAxx, light 4-betting is generally incorrect.
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Against a player who 3-bets a wide range (speculative and bluff hands), light 4-betting becomes attractive.
The logic is simple:
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If Villain rarely holds AAxx,
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and your hand performs well versus non-AAxx ranges,
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inflating the pot removes positional disadvantage and reduces Villain’s implied odds.
Additionally, holding an ace reduces the probability Villain holds AAxx by half, which further supports selective light 4-betting.
Defining a “Loose” 3-Betting Range
Using combinatorial analysis (via ProPokerTools), Bugs establishes benchmarks:
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~2.5% 3-bet → likely only AAxx.
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~5% 3-bet → balanced premium range (AAxx + premium Broadway + strong speculative hands).
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~6.5–7% → includes all AAxx and strong non-AAxx hands.
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10%+ → clearly wide, including medium/rough speculative hands.
This statistical framework allows you to decide whether light 4-betting is justified.
If a player’s 3-bet percentage exceeds the 5–7% “premium threshold,” you can reasonably assume significant non-AAxx content in his range.
A Core Light 4-Betting Range
Against loose 3-bettors, Bugs proposes a structured expansion beyond AAxx.
Core 4-betting range:
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All AAxx.
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Premium non-AAxx high-card hands such as AKKx, AQQx, and strong AKxx—preferably suited to the ace and Broadway-heavy.
Conceptually, this is similar to 4-betting KK/QQ/AK in Hold’em rather than only AA.
This range:
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Is still heavily weighted toward AAxx.
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Contains a small percentage of premium non-AAxx hands for balance and pressure.
Facing a 5-Bet After Light 4-Betting
With 100BB stacks, calling a 5-bet is a pot-odds decision.
Required equity: ~31%.
Premium double-suited AKKx/AQQx/AKxx hands:
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Are slightly profitable or near break-even versus random AAxx.
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Become slightly worse versus only premium AAxx.
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Still do not create large EV errors either way.
Conclusion: You can call without fear of major mistakes, especially if Villain sometimes 5-bets wider than AAxx.
What Light 4-Betting Accomplishes
Light 4-betting:
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Reduces opponents’ implied odds.
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Simplifies postflop play (often allowing automatic flop shoves).
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Reduces positional disadvantage.
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Forces opponents to adjust (which may benefit you).
Even small equity shifts matter when stacks are committed so early.
Part II: Defending Against a 4-Bet (Likely AAxx)
This is the more common and practically important scenario.
Core Defensive Strategy
When facing a 4-bet with 100BB stacks:
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Assume Villain has AAxx.
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5-bet AAxx all-in.
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Call with hands that:
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Perform well against AAxx.
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Can commit profitably on flops with ≥31% equity.
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Postflop plan: commit on flops where equity meets the threshold; fold otherwise.
Mathematical Model for Calling a 4-Bet
After calling a 4-bet:
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25.5BB invested.
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31% equity needed to call flop shove.
EV formula balances:
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Flops where you fold.
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Flops where you commit with sufficient equity.
This framework allows precise comparison of hand types.
Which Hands Can Call a 4-Bet?
1. Value 3-Bet Hands
High Double Pairs (Double-Suited)
Hands like strong KKxx/QQxx/JJxx with connectivity:
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Often profitable calls.
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Perform better when double-suited.
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Lower pairs sometimes outperform higher pairs due to reduced straight-blocking from AAxx.
Single-Suited High Pairs
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Frequently marginal or negative EV.
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Suitedness is critical.
Ace-Heavy Hands (Axxx)
These perform poorly:
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Effectively become 3-card hands versus AAxx.
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Unpaired ace-high Broadway wraps should be folded.
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AKKx and similar hands struggle unless very well coordinated and double-suited.
Conclusion: Most Axxx hands should fold.
2. Speculative 3-Bet Hands
Suited Rundowns
These are extremely robust versus AAxx.
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Double-suited rundowns perform very well.
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Even single-suited versions are profitable.
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Gaps matter far less than expected.
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Straight potential not blocked by AAxx is crucial.
Suited Ace + Rundown
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Double-suited versions are profitable.
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Single-suited versions are marginal.
Conclusion: Rundowns are ideal 4-bet defense hands.
3. Bluff 3-Bet Hands
Even rough but suited and coordinated rundowns perform surprisingly well against AAxx in 4-bet pots.
However:
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Their robustness applies specifically heads-up versus AAxx.
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In multiway pots, limited nut potential becomes problematic.
Example: Counting Outs vs Top Set
Bugs illustrates defensive logic with a flop example:
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Pair + flush draw + gutshot versus likely top set.
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Some outs are dead.
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Discount outs to account for Villain improving.
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Adjust to reflect realistic equity (~35% in example).
Key takeaway: calm, rational equity estimation is critical in high-variance spots.
Multiway 4-Bet + 5-Bet Scenario
An important advanced insight:
When two opponents both likely hold AAxx in a 3-way all-in:
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They block each other’s outs.
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A coordinated speculative hand can become a favorite.
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Required equity may be only ~29%.
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Certain speculative hands have 40%+ equity.
This makes calling extremely profitable, even with hands that look weak at first glance.
Major Strategic Conclusions
1. 4-Betting
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Expand beyond AAxx only against loose 3-bettors.
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Use ace blockers strategically.
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Keep range heavily weighted toward AAxx.
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Accept small EV edges when calling 5-bets.
2. Defending Against 4-Bets
Call with:
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Double-suited high pairs with connectivity.
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Suited, coordinated rundowns (especially double-suited).
Fold:
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Most unpaired Axxx.
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Weak, uncoordinated pairs.
3. Rundowns Are Structurally Strong
Rundowns:
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Hit many flops.
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Retain equity against AAxx.
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Are ideal tools for defending against 4-bets.
4. Suitedness Matters
Double-suited hands frequently swing from marginal to clearly profitable.
Final Thoughts
Chapter 5 closes the preflop portion of the series by demonstrating that 4-bet situations with 100BB stacks are largely mechanical:
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Know the equity threshold.
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Know which structures perform well.
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Commit correctly.
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Accept variance calmly.
Bugs emphasizes repetition and disciplined execution over creativity. Once the math is understood, 4-bet play becomes one of the cleaner and more manageable areas of PLO strategy.