Black's weakened queenside is an important factor in this position.

26. Kf3 The immediate 26. Na4 b5 27. Nc3 b4 28. axb4 axb4 29. Na2 Nc6 30. Kf3 would allow 30... g5! as was pointed out by GM Alexander Baburin in Chess Today. 26... Kf8 27. Na4 b5 28. Nc3 b4 29. axb4 axb4 30. Na2 Nc6 31. Ke4 The black pawn is doomed and in knight endings this is almost as decisive as in pawn endings. 31... f6 32. exf6 gxf6 33. Kd3 Ke7 34. Kc4 Kd6 35. Nxb4 Ne7 36. Nc2 Nd5 37. Kd4 e5+ 38. fxe5+ fxe5+ 39. Ke4 Ke6 40. Ne3 Nb4 41. Nc4 Nc6 42. g4 Kf6 43. h4 h6 44. Ne3 Kg6 45. Kd5 e4 46. Kxc6 1-0