14.Qxb4 opens lines on the queenside for black's attack. It also allows 14...d5! hitting the center and attacking the queen at the same time. After (for example) 15.Qd2 d4! 16.Bf2 Bxg5 Black is close to winning.
Sicilian Defence, Najdorf, English Attack
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1. Often in the Dragon/Najdorf/Scheveningan ( in lines where white goes 0-0-0), white often has to be careful about plucking a black pawn on the queenside as this gives Black open files to the white king.
2. In this position, white's g5 pawn is also being attacked twice by the black bishop/queen battery.
3. White needs to be careful about a possible discovery w/d5.
In this line why doesn't white take the undefended pawn?
Thanks!