Chelsea goalkeeper Petr Cech can't explain Manchester City's edge on them.
City have been Chelsea's nemesis in recent years. They have won five of their last eight League meetings and beat them in FA Cup semi-final and Community Shield last season.
"I don't know why," Cech told the London Evening Standard.
"We have done well at home but when we have played them at the Etihad, the games have been very tight and they have always managed to get the goals to win the game.
"City have a very good team with a lot of experience. Big players always raise themselves for the big occasions and their team have matured.
"They have played well at home this season but have found it harder away and lost a couple of games. But they won at West Ham last time and it was a brilliant performance overall.
"This is a big game for us. It will not decide the title race but it can give us a points advantage over one of our rivals if we win and we want to stay close to Arsenal."
