Many reference Antonio Conte's tactical switch away to Arsenal in September 2016 that changed everything for Chelsea's title hopes that season.
Despite losing the game convincingly, it would be the following weekend against Hull when Conte's men would begin a 13-match winning streak that propelled an uncertain season into one of Chelsea's finest.
Thomas Tuchel arguably enacted something similar when he arrived at Stamford Bridge 12 months ago, placing Chelsea into a 3-4-2-1 formation that would see the Blues go from ninth in the Premier League to European Champions in four months time.