comment: A good move, preventing the threat of e4-e5+.
context: 1. g1f3  1... d7d5  2. g2g3  2... c7c5  3. f1g2  3... b8c6  4. d2d4  4... g8f6  5. e1g1  5... e7e6  6. c2c4  6... d5c4  7. d4c5  7... d8d1  8. f1d1  8... f8c5  9. b1d2 Interestingly, yesterday's Game of the Day also featured this position. Arjun, however, played the solid 9...c3. 9... b7b5 A more or less fresh idea, played in ten games, much less than the number of games played in the main line. But Harikrishna hardly failed to notice in his preparation that Warmerdam had played this before. Actually, Harikrishna himself has played this position with White. 10. a2a4 This move is played in most games. This is understandable, since after 10.Ne5 (the engine's first choice), Black has compensation, at least to human eyes. 10... c8a6  11. f3g5 Harikrishn follows his previous experience. 11... f6d5 This is absolutely forced. 12. d2e4  12... c5b4 Necessary. 13. g5f7 A new move. I wonder whether Harikrishna had prepared this when analyzing his blitz game against Ganguly. In this game, he spent some time trying to remember the lines. 13... e8f7 Warmerdam evidently was ready for the knight sac and kept blitzing his moves. 14. e4g5  14... f7f6  15. g5e6 This is the point of White's play. 15... c6e7 Again played quickly. 16. a4b5  16... a6b7 Black's moves after the knight sac were all forced. Now, White has a difficult choice. 17. e6d4 This move, I think, took Warmerdam by surprise since he thought for more than 40 minutes on his reply.