5...Qc8 6.Be3 Nf4 7.Qb3 h5 8.Qc4 h4 9.Nf5! Bxf5 10.exf5 Qxf5 11.Bxf4 exf4 12.Bxc6 bxc6 13.Qxc6 Red8 14.Rad1
Preparing a pawn storm on the queenside with b2-b4 and a2-a4. 1.a3?! is less precise, since after1...f6 2.b4 Nf7 White will have to spend one more tempo protecting the b-pawn before he can push a3-a4.