1.Nf3 f6 2.e3 e6 3.Nd4 c6

White can start now a strong attack with 4.Nb5.

Another possibility is 4.Nc3 b5 (or 4...Nh6 5.Be2 Ng4 6.Bxg4 f5) 5.Nf5 exf5 6.Nd5 Bb4 7.Bxb5.