Strategy Deviations
When to break the rules of Basic Strategy to gain an extra edge.
What are Strategy Deviations?
Strategy deviations (also called "index plays") are situations where you intentionally break basic strategy rules based on the true count. When the count is high or low enough, the mathematically correct play changes.
The "Illustrious 18" are the 18 most profitable deviations, identified by Don Schlesinger. These account for the vast majority of the extra profit from playing deviations.
The Illustrious 18
These are the 18 most important strategy variations based on the True Count. The "Index" is the True Count at which you should deviate from Basic Strategy.
| Player Hand | Dealer Upcard | True Count Index | Deviation Action |
|---|---|---|---|
| Insurance | A | ≥ +3 | Take Insurance |
| 16 | 10 | ≥ +0 | Stand |
| 15 | 10 | ≥ +4 | Stand |
| 10,10 | 5 | ≥ +5 | Split |
| 10,10 | 6 | ≥ +4 | Split |
| 12 | 3 | ≥ +2 | Stand |
| 12 | 2 | ≥ +3 | Stand |
| 11 | A | ≥ +1 | Double |
| 9 | 2 | ≥ +1 | Double |
| 10 | A | ≥ +4 | Double |
| 9 | 7 | ≥ +3 | Double |
| 16 | 9 | ≥ +5 | Stand |
| 13 | 2 | ≥ -1 | Stand |
| 12 | 4 | ≥ 0 | Stand |
| 12 | 5 | ≥ -2 | Stand |
| 12 | 6 | ≥ -1 | Stand |
| 13 | 3 | ≥ -2 | Stand |
How It Improves Your Odds
Card Counting Without Deviations:
Player edge: +0.5% to +1%
With Illustrious 18 Deviations:
Player edge: +1% to +1.5% (+20-30% more profit!)
Deviations are the final piece of the puzzle. They squeeze out every last bit of advantage from favorable situations, turning a good counter into a great one.
Why it Works
Basic strategy is optimized for a neutral deck. When the count changes dramatically, the composition of remaining cards changes, making certain plays more or less profitable. Deviations exploit these shifts to make the mathematically optimal decision in each situation.