Chubukov: How it Helps, and How it Doesn't
Sklanksy-Chubukov is an endgame table that tells you the deepest you can jam a hand from the small blind and still be sure your expectation is better than folding. That sounds like something useful to have in your arsenal, but hidden in that explanation is the fact that to be sure you have better expectation from going all-in than folding, you have to evaluate the expectation from jamming as if your opponent plays perfectly against your all-in, as if you accidentally flipped over your cards (or are playing on Ultimate Bet), and your opponent knows what you have. That means if you go all in with 87s, your opponent will fold 76s, but call with 92o. This means that Chubukov provides some useful information, and a lot of useless information.
The biggest mistake players make when learning about Chubukov is treating it as a strategy to employ against certain opponents. Chubukov is meant to be information, not a strategy. When we ask Chubukov whether we are guaranteed to be +EV when we go all-in for 8bb with 98s, the answer will be “no”, but that says close to nothing about whether 98s is actually a good enough hand to go all-in with at this stack depth.
Chubukov is not a strategy. It tells you that 98s is a jam for sure up to 7.7bb, and then expects you, the human, to be smart enough to know that because 98s is a hand in which opponents play drastically different against you than they would if they didn't know your hand, that this information is not particularly useful. Against the vast majority of opponents, even those with very loose calling ranges, 98s is an easy all-in for ten big blinds.
So, what is Chubukov? I think the best way to think about it is that Chubukov is the first thing to check to see if you are being way too conservative with your weak Ax, Kx, Qx, and low pocket pair hands from the button. While the information for 54s is fairly useless (we are to assume our opponent is calling with 62o?), there are reduced problems with assuming a perfect calling range for those types of holdings.
To illustrate this point, here is a quick quiz. We're playing against an opponent who jams fairly wide over limps and minraises, but not so wide that we feel like limp/calling or minraise/calling is the best option. For each of the following situations, consider going all-in from the button. Is this play:
A) Guaranteed to be better than folding, or
B) Depending on our opponent's calling range, possible to be -EV when compared with folding?
1. 22 24bb deep
2. Q5o 7.5bb deep
3. Q2s 8bb deep
4. K3o 10bb deep
5. K3s 14bb deep
6. A2o 22bb deep
The answer to the six questions is that they are all guaranteed to be +EV jams. If you ever openfold K3o at 10bb or Q5o at 7.5bb, you're losing money in that hand compared against openshoving, period, no matter how loose or tight or downright weird his calling range is. That is useful information. Sometimes we know our opponent is calling looser than NASH, but NASH doesn't tell us if we can still jam our hand and be +EV despite that. Chubukov is a quick place to check to confirm that yes, in fact, just because your opponent is playing oddly and you can just feel yourself about to be snapped off by Q6o 7.5bb deep, you should still go all-in with Q5o. The power of your queen high makes it so even if your hand was flipped up, it is still good enough to go all-in with.
However, we still need a couple of caveats. The reverse is not true – if Chubukov says that we cannot profitably go all-in if our opponent knows our cards, that does not answer the question of what to do given that he does not. Basically, Chubukov is just a "sanity check" for when you are playing against a loose opponent and even though NASH says it's a jam, you are not sure against his calling range. In this case, Chubukov can restore your sanity by saying “yes”, but when it says “no”, you have to use your human brain to make the decision. Additionally, remember that comparing to folding is often a metric that is too generous. In the above examples, going all-in is better than folding with A2o 22bb deep, but in reality, A2o is only an openjam up to around 15bb. This is because the best comparison with A2o is minraising deeper than 15bb, where our expectation will be significantly better than -0.5bb from folding.
Chubukov tells you that you can always shove K3o for 10bb and do better than folding, even against an opponent with a crazy calling range. It tells you that the same is true for Q2s at 8bb, and Ax hands way above any stack depth you would consider going all-in for. Take these insights, and if you start to get confused about the rest, it is probably best to leave it behind and focus on studying that actually gives good insight into better strategic adjustments.