City overcame a 2-1 deficit to beat Southampton 3-2 last Sunday and Mancini has said that his players were "bad" on the day.
"We always play a tough match in the second game," PA Sport quotes Mancini as saying. "Liverpool will be a very strong game."
"[Against Southampton] we played a bad game, we were not a team. We were 10 players that tried to score. We showed our character but we didn't play as a team.
"This could be normal in the first game but if we want to win, we have to play as a team."
Liverpool won the away leg of their Europa league qualifying playoff 1-0 against Hearts last night.