By Trevor Steven When it comes to the greatest managers in Premier League history, two men are out there on their own: Sir Alex Ferguson and, following Manchester City’s sixth title in seven years, Pep Guardiola. Fergie set the bar, winning 13 championships in 26 years at Manchester United, and now Guardiola is matching it. Those two are the best we have ever seen; no one else comes anywhere near. It’s difficult to compare teams from different eras because the Premier League has evolved. It is now stronger than ever, with perhaps eight different teams who will start next season believing that …