Former Arsenal manager Unai Emery came back to haunt his former club this weekend, and put an enormous dent in their Premier League title ambitions in the process. But after a first-half where Mikel Arteta's men looked in total control, how did his predecessor completely flip the game around in the second 45? Adam Clery looks at how a slight change of shape, and a massive change of approach, gave us one of the shocks of the season.