Coach Sir Alex Ferguson recognized the opponent's club of his main team.
The teams will meet on Monday in a crucial match of the English Premier League, which could determine the outcome of the fight for the first place.
"They are our direct opponents. Man City competes with us for trophies," said Ferguson. "We have to get used to the fact that matches against Man City will be of special importance."
For many years, the second Manchester club, which has not yet won any Premier League trophies, has not come close to Man Utd. However, the hundreds of millions invested in strengthening the squad have changed this situation.
"If we continue to compete for the top positions - which I think we will - the matches against Man City will be just as important as those against Liverpool. Perhaps not as emotional, as there is no lack of emotions against the Liverpool team, but at least at the moment more significant in another aspect," Ferguson said.