Trading the pieces you opened lines for
1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.d4 exd4 5.Nxd4 Nxd4 6.Qxd4 Qf6
- The mistake
- Playing 4.d4 and then recapturing on d4 with the knight and the queen, to keep the pawn count level.
- Why it costs
- 4.d4 is played to open the centre while White is the better developed side. Trading the knights and bringing the queen out to be met by 6…Qf6 undoes both halves of that: the pieces that were ahead have left the board, the queens follow them, and the bishop on c4 has nothing to look at.
- Instead
- 5.c3, giving the pawn back for the centre and the initiative, or 5.O-O with the Max Lange in mind. If neither appeals, play 4.d3 and take the slow game on purpose.