Part: Part Five - Betting Before the Flop

Out of the small blind

Pre-flop
Blinds 100 / 200Pot 800 (4 BB)SBA♣9♦● 25,000 (125 BB)YOUto actBTN● 25,000 (125 BB)Buttonraises 500 (2.5 BB)BB● 25,000 (125 BB)yet to actD

A button player opens to 500 to steal. It folds to you in the small blind with A♣9♦, and the big blind is still behind you.

Button steals; you hold A♣9♦ in the small blind. Best?

WhyThree-bet (or fold the weakest hands). From the small blind you'll be out of position all hand and the big blind can still wake up, so flatting is the worst option. Against a button steal, A-9 offsuit is a fine re-steal - take it down or play with the initiative.
What happensYou three-bet to 1,700 (8.5 BB); both fold.  You win it pre-flop.
In the small blind you avoided the out-of-position flat-call trap and three-bet instead - against a wide button steal, re-stealing beats calling and letting the big blind in.

From the small blind, prefer three-betting or folding to flat-calling - being out of position with a player still behind makes calling the weakest choice.