And Black regains the pawn.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5 Nakamura decided to stick to the Ruy Lopez, but today his approach will be different. 3... a7a6  4. b5a4  4... g8f6  5. e1g1  5... f8e7  6. f1e1  6... b7b5  7. a4b3  7... e8g8  8. h2h3  8... c8b7  9. d2d3  9... d7d5 Aronian is ready to play the Marshall, even against the Anti-Marshall. According to Megabase, this move is recently more successful than 9...d6. 10. e4d5  10... f6d5  11. a2a4  11... c6d4  12. b1d2  12... d4b3  13. d2b3  13... d5b4  14. f3e5  14... d8d5  15. f2f3  15... e7d6  16. d3d4  16... a8e8 All of this is theory, and as usual, Black is getting enough for the pawn thanks to his active pieces and the bishop pair. 17. a4b5  17... a6b5  18. c1d2 On the other hand, Nakamura's approach is very pragmatic. Take the pawn and let the opponent be creative in finding counter-play, when also low on time. 18... b4c6 Aronian banged out this novelty, but it will remain a secret if he had intended to do so, or simply if he messed up the lines. 19. d2f4  19... g8h8 Prophylaxis against the possible fork on the e7-square. 20. f4h2 Prophylaxis in return, as the bishop needs protection.