The  weak point on f2 needs overprotection.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1c4  3... f8c5  4. c2c3  4... g8f6  5. d2d3  5... d7d6  6. e1g1  6... a7a6  7. a2a4  7... c5a7  8. f1e1  8... e8g8  9. h2h3  9... c8e6  10. c4e6  10... f7e6  11. b2b4 A fashionable line at the top level these days. It  seems as Black should have rich counterplay along the semi-open f-file but things are not as simple. 11... f6h5  12. a1a2  12... d8e8  13. b1a3  13... h5f4  14. c1f4  14... f8f4  15. a3c4  15... e8g6  16. b4b5  16... a8f8 Just in time to transfer the rook to the  correct side of the board and avoid the consequences of the pin along the  a-file. 17. c4d2  17... c6e7  18. d3d4 Once again hoping to lock the bishop. 18... g6f6 To which Grischuk strongly disagrees. 19. d4e5  19... d6e5  20. b5a6  20... b7a6  21. d1e2 Finally, Caruana could not solve the  problem of the a7-g1 diagonal, but at least created some weaknesses to  work on. Strategically, White should have the advantage because of the  crippled black pawn structure but the continuous delicacy of the white  king's position makes the game roughly balanced. 21... a6a5 