Manchester City midfielder Ilkay Gundogan says last night's Carabao Cup defeat at Southampton cannot be repeated.
City face Manchester United on Saturday at Old Trafford.
Gundogan warned: "Today's United are probably the strongest in a long time.
"Now the team looks very confident, plays excellent football. We will need to perform much better than today to achieve the right result."
City go into the game in second place with 39 points, United are fourth with 35 points.
