If the past decade of English football has one unifying theme it is tactical renewal.
Since the mid-2010s - and since Antonio Conte, Pep Guardiola and Jurgen Klopp - the Premier League has attracted Europe's best coaches, putting a once sleepy and unsophisticated division at the vanguard of tactical innovation.
But we are in a moment of flux. New ideas still flood into the league but nothing, yet, has emerged as the next great theory. As Guardiola treads water at Manchester City we are waiting to find out where the sport goes next.
Here are some ideas - some quirkier than others - for where the game could go next.