3
[FEN "r2qk2r/pQpbbppp/n2p1n2/3Pp3/4P3/2N1BN2/PPP2PPP/R3KB1R w KQkq - 0 1"]

This position is evaluated at +6.4l but if I capture with the Bishop (Bxa6) it drops down to +0.8.

Why does the evaluation drop when I make that move?

[Title "AKP2002-moisturiser, 600+5 Rated Rapid game, lichess.org, 4/21/2020"]
[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. d4 d6 4. d5 Nb8 5. Nc3 Bg4 6. Be3 Nf6 7. Qd3 Be7 8. Qb5+ Bd7 9. Qxb7 Na6 10. Bxa6 Qb8 11. Qxb8+ Rxb8 12. O-O-O c6 13. Ng5 cxd5 14. exd5 Nxd5 15. Nxd5 Bf6 16. Nc7+ Kf8 17. Ne4 Bd8 18. Nd5 Bc6 19. Bxa7 Ra8 20. Bb8 Rxa6 21. Bxd6+ Ke8 22. Nc7+ Bxc7 23. Bxc7 Ke7 24. Bd6+ Ke6 25. Nc5+ Kf5 26. Nxa6 Rc8 27. Rhe1 Re8 28. Nc7 Rd8 1-0

Why isn’t capturing with the Bishop good, since it brings more attackers into play, and is hence better move?

Brian Towers
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1 Answers1

7

Why is the engine evaluating against bringing more attackers in this position?

That's not what it is doing. It is evaluating against blundering a draw. After Rb8 your queen has nowhere to go apart from allowing a repetition. If you play Qxa6 you are just a piece and a pawn up for no compensation.

[FEN "r2qk2r/pQpbbppp/n2p1n2/3Pp3/4P3/2N1BN2/PPP2PPP/R3KB1R w KQkq - 0 1"]

1. Bxa6 (1. Qxa6) Rb8 2. Qxa7 Ra8 3. Qb7 Rb8=
Brian Towers
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  • While 10.Bxa6 is a clear blunder, it doesn't technically blunder into a draw. After 10...Rb8 11.Qxa7 Ra8 12.Qb7 Rb8 13.Qb3 Rxb3 14.axb3, Stockfish gives White an advantage. – Inertial Ignorance Apr 26 '20 at 12:51