Part: Part Five - Betting Before the Flop
Isolating a limper
Pre-flop
A weak, passive player limps in from middle position and it folds to you on the button with A♣J♦.
A weak limper, and you hold A♣J♦ on the button. Best?
WhyA passive player's limp usually caps him at a speculative or weak hand, and A-J dominates most of it - raising isolates him heads-up and in position where your edge is largest. Limping along behind just builds a multiway pot and throws away the advantage his weakness handed you.
What happensYou make it 900 (4.5 BB), the limper calls, the blinds fold. Pot: 2,100 (10.5 BB). You've got exactly what you wanted - heads-up, in position, against a player who's already shown weakness.
Flop
Flop A♦ 7♣ 3♥ - top pair, good kicker. The limper checks.
Top pair, good kicker, heads-up and in position. Best?
WhyYou raised to play precisely this pot: heads-up with the best hand against a weak opponent. On a dry A-7-3 he'll pay with worse aces and middling pairs, so charge them - checking back only lets a free card in and wins nothing.
What happensYou bet 1,200, he calls, then folds the turn. Top pair against a weak limper won't always reach showdown, but you pried a bet out of a worse hand - which is the entire point of isolating him.
You raised to punish a limper's weakness, got heads-up and in position with the better hand, then banked value when you flopped top pair. Isolation raises convert a limper's passivity into your profit.
A weak limper is an invitation - raise to isolate with a dominating hand, getting heads-up and in position instead of drifting into a cheap multiway pot where your edge shrinks.