Manchester City manager Pep Guardiola has named Jurgen Klopp's Liverpool and Luis Enrique's Barcelona as the two toughest sides he has ever faced in management.
Unfortunately for Guardiola, he will be up against one of those sides on Sunday when the Premier League champions visit the Etihad for their first meeting of the season.
While City's form has been sporadic in the opening stages of the campaign, Liverpool have largely remained consistent and already look the favourites to lift the title once again.
A victory over the Blues would see Jurgen Klopp's side stretch their lead on City to eight points, which could be a significant margin despite it being so early in the season - though City do have a game in hand.
Ahead of the encounter Guardiola was asked which fixtures had been the most challenging for him as a coach, with Liverpool and the treble-winning Barcelona of 2015 standing out.
"I will never underestimate an opponent," he said. "When I was in Bayern Munich there was Dortmund with Thomas Tuchel or Jurgen that were incredible teams, when I was in Barcelona Real Madrid were so, so tough always but here since I arrived when we fought for the titles Liverpool were the big rivals.
"I have faced many teams, I have incredible respect for all of them but this is my feeling that Liverpool in the last few years and Luis Enrique's Barcelona when I played them in Champions League semi-finals with Bayern Munich are the toughest opponents I have ever faced.
"I will try to beat them but that is part of the process. Maybe in a few years City will have another rival or Liverpool will have another rival so this will not be eternal in terms of all the teams being there but in the last there years the toughest opponent we have had in the Premier League has been Liverpool."
