Roberto Mancini says Manchester City cannot afford to lose Sunday's derby against Manchester United at the Etihad.
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The defending champions go into the game three points behind league leaders United, and Mancini fears a six-point gap between the two could prove crucial.
"They can lose because they have three points more. We have three points less and we can't lose," he said. "I think they are better than us in this moment, but a derby is a derby.
"They have a small advantage, but a derby is a really difficult match for both teams. United are favourites [for the title] but this is not the [whole] season because we have seven months afterwards."
Mancini hopes playmaker David Silva will recover from a hamstring injury and will give fitness tests to James Milner and Gael Clichy on Sunday morning.
However, Aleksandar Kolarov's ankle injury will rule him out, and Micah Richards remains sidelined.
Mancini believes United are a superior team after their summer acquisitions of Robin van Persie - who had been a target for City - and Shinji Kagawa.
"They were a strong team, and then they bought Van Persie and Kagawa. They put another 25 goals into the squad," he said.
City won both Manchester derbies last season, including a 6-1 victory at Old Trafford that Mancini said had been a season-changing match.
He added: "It was important for us because we played the first derby away and we won 6-1. There are some important games than can change your season, and the derby was one of the first games like this for us."