comment: This move has never been played before, according to my database. Black wants to continue the thematic development of the bishop on a6.
context: 1. d2d4  1... d7d5  2. c2c4  2... c7c6  3. g1f3  3... g8f6  4. b1c3  4... e7e6  5. c1g5  5... b8d7 The safest option for Black, taking the game to the Orthodox Defense. 6. e2e3  6... d8a5 The Cambridge Springs Variation has a vast legacy and was employed in the magnificent 1927 match between Capablanca and Alekhine. 7. c4d5  7... f6d5  8. d1d2  8... f8b4  9. a1c1  9... h7h6  10. g5h4  10... e8g8 10...b6 and 10...c5 are important alternatives. 11. a2a3  11... b4c3  12. b2c3  12... d5f6 A rare move. The players with Black usually accept the pawn sacrifice. 13. f1d3 