City are pursuing a third consecutive Premier League title, but a shock 3-2 loss at Norwich City last weekend, left them five points behind the Reds.
Speaking ahead of Saturday’s home game against Watford, the former Barca and Bayern Munich boss said: “You have to understand what we have done in the past does not ensure you can do it tomorrow or the day after.
“The opponents we have, I’ve said many times, are the strongest opponents I have faced in my career as a manager – Liverpool.
“These are not weak words. I said it when they were in front, I said it when we were in front; when we won and we lose.
“They have absolutely everything in terms of a positional game, counter-attack, set pieces, transitions, offensive, defensive and mentality. Anfield the stadium – many things.
“I know how difficult it was, how difficult it is and how difficult it will be.
“But that is the challenge. The same with the central defenders. We go, ‘Okay, let’s find a solution to keep the team stable and good’.”