The above diagram shows the position after Yefim Treger's 15.Rxe4. I played the incorrect 15...Bf5 16.Ra4 a6 after which Treger missed the win of a pawn by 17.Rb1. On move fifteen, Black could have improved by 15...b5, 15...g6, or even 15...Bd7 with the idea of 16...Bc6.