The "Extra" Piece
“Extra Piece”… I think prominent chess coach Mark Dvoretsky coined this term. Let's say white has a great square in the center, which is defended and supported by a pawn and cannot be attacked by the opponent’s pawns. Naturally, white would like to put one of his pieces on this square. If there are two knights that want to get to the square, then only one will reach it, while the other has to settle for a less promising square. This piece is called an “extra” piece because it has to wait when the other piece, which occupies this great square, will move or will get traded. Dvoretsky’s concept is for the weaker side not to allow the trade of an “extra” piece- to keep it out of play.
Lets look at specific examples. White just played Nd5, threatening N:c7 and placing the knight on the most active square. White has an “extra” knight on c3, which is waiting for the d5 square to get free. So, according to Dvoretsky it is unfavorably for black to trade Nd5.
It is interesting, that eventually black traded white’s “extra” knight. But black did it in the most favorable situation: when Ne8 seemed not to have any good prospects. In reality, after g6 and Ng7, he could have jumped either to f5 or h5.
In the next example black’s “extra” knight does not find any peace during the whole game, not even in the endgame can he find a good square to rest. White is better: his pieces are more concentrated around black’s king, f7 is a potential big weakness, d5 in the endgame will be isolated, and black’s rooks are rather passive.
The third example features the Nc3-Nd5 couple, so black does not want to trade any of white’s knights for now. Black has great prospects for attack on the b-file. White would need to waste a tempo to take on c4, therefore black has all the time in the world to take away Nf6 and to chase away the Nd5 with e6.
Overall, when the opponent has “extra” piece one should always consider taking it as well as leaving it there and playing around it. As in the above examples, the opponent’s one knight might be very active in the centre, while the other knight is completely out of play. It is ideal for the opponent to trade that bad knight. That is why one should avoid the trading active knight: so the passive knight has nowhere to go. All the examples above demonstrated this technique. At the end, one of the opponent's knights got traded but only when it was favorable for us.
