The German knows City will be tough opponents in the Champions League this week.
City face a Barca side who have won their last 11 games in all competitions. The last team to beat Barca were David Moyes' Real Sociedad side on the 4th January.
But City will be hopeful of pulling off a positive result, especially as they have already defeated Bayern Munich in the competition this season.
The German has been speaking to El Periodico this weekend and said of the upcoming fixture:
"Manchester City. They are a great team. I watched them against Bayern and we have to play our best in order to win and get to the end of the competition."
The German goalkeeper is likely to keep goal for Barca in the game. He has been the second choice stopper since arriving from Borussia Monchengladbach in the summer behind the more experienced option of Chilean stopper Claudio Bravo.
However he has been the Champions League stopper for much of the season and will be hoping to keep sticks against the Premier League champions in midweek.