Instead of the tactical 6.Bc4, White has quieter moves like 6.Be2 (diagram). Black can also continue quietly with the move 6...e6, which usually transposes into the Scheveningen Variation [ECO B84], when 7.Be3 (or 7.O-O Qc7 8.f4) 7...Qc7 is possible.
Black can also challenge White in the center with 6...e5. After 7.Nb3 Be7 8.O-O, Black has
- 8...O-O 9.Kh1 (or 9.Be3).
- 8...Be6 9.Be3 (or 9.f4).
Many players are reluctant to play ...e5 in the Najdorf, since it creates a hole on d5 together with a backward Pawn on d6. The dynamics of the position are not so straightforward.
If White plays Nd5 without preparation, Black plays ...Nxd5, closing the hole after the recapture e4xd5. In order to play Nd5, White has to recapture on d5 with a piece. This takes time to set up, because White's pieces also have to protect the Pawn on e4 plus prevent Black from playing a Knight to d4.
As for the backward Pawn on d6, Black aims to play ...d6-d5 as soon as possible. If White succeeds in preventing the ...d5 break, the Pawn on d6 is well protected by the Be7, the Queen on b6 or c7, and a Rook played to d8.
