Where players go wrong in the Philidor Defense
We looked at the games of 208 players in the Philidor Defense and found the first move that left the opening book and made their position worse. On average that move cost 1.4 pawns.
The "book" is the set of established moves strong players have settled on. A pawn here is the engine's unit of advantage: 1.0 is about the value of one pawn. Data from Blackbox Chess reports, updated 2026-11-14.
1. Nd4 on move 4, playing Black
3 players made this move here, and it cost them 1.2 pawns on average. The board shows the position just before it.
2. f6 on move 3, playing Black
3 players made this move here, and it cost them 1.0 pawns on average. The board shows the position just before it.
3. Nc3 on move 4, playing White
3 players made this move here, and it cost them 0.8 pawns on average. The board shows the position just before it.
By rating
| Player rating | Players | Average cost of the first mistake |
|---|---|---|
| Under 1000 | 106 | 1.6 pawns |
| 1000 to 1399 | 49 | 1.1 pawns |
| 1400 to 1799 | 32 | 1.1 pawns |
| 1800 and up | 21 | 1.2 pawns |
These are other players' games. See where you leave the book in yours: your first 10 games are free, with no account needed.
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