In the BB position, the mainstream strategy is to defend the BB with a fairly wide range, because you have already invested 1BB, the odds are good, and you are the last to act preflop.
In this article, we will look at these reasons in more detail. Let’s assume
the effective stack is 10BB.
◆The BB 
holds the hand, and the SB folds to a minimum open-raise from the BTN.
In this situation, the BB has three options:
1 Fold
2 Call
3 Raise All-in
First, I’ll fold 1. Although this hand doesn’t have any high cards, it’s a suited connector, so it’s an easy hand to handle.
Therefore, folding this hand would be a waste in terms of hand equity.
Next, regarding the 3 raise all-in, in this situation the player on the BTN is raising to the short-stacked BB, so unless he open-raised extremely loosely, I don’t think he’ll fold in response to our raise all-in.
In other words, in this situation, it’s not much different from receiving an open all-in of 10BB.
Therefore, we need a hand that can withstand an all-in request from our opponent, so this is a little short.
Now let’s consider calling with 2.
Since the BTN player min-raised, the BB can see the flop with just one more BB investment, and the odds for calling are very good.
And because your hand is a suited connector, you can easily draw, and in addition to a pair on the flop, you can attack your opponent’s CB with a gutshot or better draw. And on a flop like this, where you completely miss, you can easily fold, saving the rest of your stack compared to if you had gone all-in pre-flop. And with
a 
short
stack like this, the play is easy: you either fold on the flop or go all-in.
What if you’re in the same situation with a 30BB effective stack? While it’s still a manageable hand, it’s more difficult to play than it was with 10BB.
For example , if you get a flop like this, you might be able to call the cornerback on the flop, but unless you get a 6 or 7 on the turn, you’ll be folding to your opponent’s second barrel. And because your stack is deeper, your position disadvantage becomes greater, making the showdown more difficult and making it harder to realize your equity. 
For these reasons, defending the big blind is an effective strategy, especially when the stack is around 10 big blinds.
Let’s take a closer look at this with some example board textures.
◆The BB holds the hand, and the SB folds to a minimum open-raise from the BTN. The effective stack is 8BB.
Let’s assume the BTN’s opening range is 37.25%.
The SPR on the flop will be approximately 1.
●
On a flop like this, your equity is only about 10% against the BTN’s opening range.
This is an easy situation to check-fold.
Since your effective stack is 8BB, even if you were all-in preflop, your opponent would almost 100% call.
So you can consider that you have saved the remaining 6BB.
●
This flop gives us a gutshot and a backdoor flush draw, so it’s not a bad flop.
We have 36% equity against our opponent’s range.
This may feel a little disappointing, but the SPR on the flop is almost 1, so we have the equity to call our opponent’s all-in.
However, with a hand like this, it’s best to lead bet all-in to consider fold equity.
We can fold most of the two-overcard hands in our opponent’s range, and they may fold weaker pairs out of caution against our top pair.
●
This flop is very favorable for us.
Of course, we are losing to our opponent’s overpairs, but we still have about 70% equity against their range.
Regarding the flop action, I think we can either lead bet all-in or check.
By going all-in, we can protect our equity by forcing hands like two overcards without an Ace to fold, or we can get them to call with a pair hand of 66 or lower or an Ace with a strong kicker, putting us in a favorable position.
If our opponent checks in response to our check, we will give them a free card, but they may be able to stack off with a weaker hand than if we had gone all-in.
However, if we go all-in with a lead bet even with a draw, it is effective to mix it with a made hand like this.
●
This flop can also be considered a good flop.
You hit a middle pair, and you have about 56% equity against your opponent’s range.
It’s difficult to decide whether to lead-bet all-in or check in this situation, but I think either is correct.
However, on a board like this, if you go all-in, you could end up folding your opponent’s made hand, which you’re winning. It depends
on how often your opponent bets back, but in this case, I think a check-raise all-in has a higher expected value.
