Tarrasch Variation, Open System, Shaposhnikov Gambit

In the Shaposhnikov Gambit, Black does not recapture on d5 with 4...exd5 or 4...Qxd5, the two standard recaptures. Black plays 4...Nf6 instead, developing the kingside knight first and leaving White a pawn ahead. White's extra material comes as doubled pawns on d4 and d5, and both pawns are exposed to the black pieces and to the pawns on c5 and e6. Black is betting that regaining the pawn later, or simply developing faster, makes up for the material.