Santi Cazorla is good enough to play in a central midfield position or from the wing, and another signing for the midfield would have allowed Wenger to rotate Cazorla and Lukas Podolski in the position on the left side of attack.
Cazorla offers far more creativity, but Podolski has been outstanding in front of goal this season. The variance in style that both players offer is exactly what Arsenal needed for the attacking positions and one of the key reasons why Wenger should have strengthened his attack.
