The "incredible history" of Manchester United should serve as a warning that the Carabao Cup semi-final is not yet over, according to Blues boss Pep Guardiola.
Manchester City won 3-1 at Old Trafford three weeks ago to take control of the semi-final, but Guardiola is refusing to consider that the tie might be beyond an injury-hit United already.
With the Carabao Cup abandoning the away goals rule it means a 2-0 victory for United would take the game to extra-time and Ole Gunnar Solskjaer has already tried to summon the spirit of Paris, where United overturned a two-goal first leg defeat to progress in the Champions League last season.
City were by far the better side at Old Trafford, but Guardiola is wary of the threat United can pose when they have their backs to the wall.
"It is Man United. They can do it. We have to do almost a perfect to go through to the semi-final," the City boss said.
"In this kind of games against this kind of teams with incredible history behind. They have pride and I know how difficult it will be to reach the final."
United won 2-1 at the Etihad in the Premier League in the first week of December, a day when they proved devastating on the counter attack.
City should be pre-warned about that threat this time and can afford to be more cautious as well thanks to their first leg advantage, but Guardiola is aware that United have nothing to lose.
"We have to be careful about their skills, careful of counter attack and set-pieces and we have to defend," he said.
"They don’t have nothing to lose so they are going to attack. We have to control emotions. We have to try to score goals."
