1. c2c4  1... e7e5  2. b1c3  2... g8f6  3. e2e3  3... d7d5  4. c4d5  4... f6d5  5. g1f3  5... b8c6  6. d1c2 It is curious that a year ago in a similar must-win situation, Carlsen chose the same opening against Nakamura to try and level the score. For several moves, the two players followed that game. 6... d5b4  7. c2b1  7... f7f5 