Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nc3/3...dxc4/4. e3/4...b5/5. Nxb5/5...cxb5/6. Qf3/6...Nc6/7. Qxc6/7...Bd7/8. Qf3/8...e5/9. dxe5/9...Bb4/10. Ke2

10.Ke2
Now, the white king and queen are lined up on the h5-d1 diagonal. Black can use this to develop with tempo. Nh6! develops and threatens Bg4. Note that the "Knight on the Rim is dim" quote doesn't apply here, as the f6-square is taken and it is wilh tempo. The King is stuck in the center. The best move is Nh6.