By Ewan Murray The Enzo Maresca era at Chelsea begins with the toughest test possible as the Blues welcome Premier League champions Manchester City to Stamford Bridge this Sunday. The Italian, who guided Leicester City to the Championship title last season, has replaced Mauricio Pochettino in the dugout and will face his former employers on his competitive Chelsea debut. However, a torrid pre-season campaign – which included a 4-2 defeat to Man City \- shows patience will be key as Maresca ushers in a new football philosophy in west London. Some things don’t change, though. Chelsea have been a…