This is a really, really basic post about pot odds and why calling with a hand that isn’t best is actually correct in many situations. If you know what pot odds are, you needn’t continue, but if you think someone calling with an inside straight draw is always a stupid player, you may want to continue. I need to get this off my chest.

Here’s the deal: An inside straight draw has, and let’s make it simple, a 10% of hitting. Look at what happens when the pot is really big and you make a small bet (e.g. a raised pot after the flop with many players in it in limit hold ‘em, for instance): If the pot is 10 bets at that point, it’s going to be 11 bets when you bet, and someone with an inside straight is investing one more bet to win 11. 10% of the time, he’ll win the pot, and 90% of the time, he’ll lose one bet.

10% of 11 bets = 1.1 bets.
90% of 1 bet = 0.9 bets.
Net gain: 0.2 bets.

So someone calling with an inside straight draw is winning money by calling. Keep that in mind next time you berate the “fish” who called with his unimproved AK on the J-T-4 flop with a 10-bet-pot, despite you “obviously” having AA. If that fish were me, and you showed me your hand, I’d still call. If you showed me your hand preflop, however, I would have folded, but that’s a different story.

Now, having understood that, and you should, I will make a slightly more advanced point that isn’t quite as easily digested: The person with A-A loses money if you call with AK on that particular flop with a pot that big.

Say what?

Yeah, the guy with the pocket rockets is a big favorite to win, and, as we said above, will go on to win the hand a large majority of the time. Still, he should prefer it if you folded instead of called with the pot this big. Why? Because if you win 0.2 bets on average, someone has to lose it, and that’s him. Does that intuitively make sense to you? Let me see if I can show you why.

When the pot is so big that a person is correct to call because of the pot odds, the person with the best hand at the moment (the hand with the largest chance to win, for stringency) should wish that the other guy actually folded. It may seem strange, but it’s true. If the pot is 10 bets, and I bet with my pair of aces, I’d want you to fold your inside straight, because what will happen is this:

100% of the time, I will win 10 bets.
Net profit: 10 bets.

If you instead call, the situation changes:
90% of the time, I will win 11 bets.
10% of the time, I will lose 1 bet.
Net profit: 9.9 - 0.1 = 9.8 bets.

That’s where the inside straight draw’s profit comes from: I lose 0.2 bets if you call.

What happens, though, if the pot isn’t big enough for you to profitably call with your inside straight? What if it’s only 5 bets? Aha, then I should be rooting for you to call! Check this out:

90% of the time, I will win 6 bets (the five in the pot, plus the one you pay to call)
10% of the time, I will lose 1 bet
Net profit: 5.4 - 0.1 = 5.3 bets. That’s a net gain of 0.3 bets, if you call instead of fold. Who loses that third of a bet? You do.

This reasoning is applicable to exactly all of poker, and thinking “GOOD HAND BET, BAD HAND FOLD” is a horribly oversimplified - not to mention incorrect - way of judging the situation. The size of the pot as compared to the amount you have to pay is the number one factor in determining how you should act with a draw.

Just so I don’t fool one of you into thinking that just because you lose money if the other guy calls, you’d be better of checking, let’s look at the first example and evaluate checking again:

90% of the time, I will win 10 bets.
10% of the time, I will lose nothing.
Net profit: 9 bets. This is a lot worse than betting.

There are tons of good books on this, so I won’t keep on with it, but I’ve seen so many wanna-be table coaches lately lecturing people saying “omg, I can’t believe you called with that!” when the call was in fact entirely correct. This is very basic stuff, and anyone playing poker should learn it.