 Nxc4 If 5...Kc6 6.Nxb6 Kxb6 7.Rxb2+, White's rook draws easily against Black's knight and bishop.6.Rxb6+ Now Black's best try is 6...Kd5!or 6...Ke7!, when the endgame of rook against two knights and a bishop is a well-established theoretical draw.