The last time Arsene Wenger played with three at the back, I was in the team alongside Tony Adams and Steve Bould at Derby in May 1997.
If you want to play with a back three, you have to know the system inside out. It is not something you can simply adapt to overnight.
We first started playing this way under Bruce Rioch. Even though we had a group of experienced central defenders, the system was initially difficult to pick up. It required walkthroughs every Monday morning in training of scenarios we might face.
Arsenal may have won on Monday night but they had a few teething problems — particularly when it came to Alvaro Negredo's equaliser.