1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... d7d5  4. g2g3 The Catalan has become a powerful weapon for Nepomniachtchi. After all the work he had to do in order to play it with Black in the match against Carlsen, no wonder he decided to try it with the other color. 4... f8b4 This check is one of the most reliable options for Black. 5. c1d2  5... b4e7  6. f1g2 