The Italian says he has no interest in his title rivals' much-hyped clash with Liverpool as he prepares for a testing trip to Arsenal on the same day.
Mancini's champions trail United by seven points at the top of the Barclays Premier League, a gap that could be 10 by the time City kick-off at the Emirates Stadium.
With a number of key players missing - including Yaya Toure, Sergio Aguero and Samir Nasri - Mancini wants to focus only on his own team and not the pressures of the title race.
He said: "We should go our way. We can't think about United or other teams.
"We don't see the table in this moment but at the end of February.
"Also it is difficult because we are missing important players but we want to do a good job on Sunday."
The Toure brothers, midfield star Yaya and defender Kolo, are preparing for the African Nations Cup with Ivory Coast, striker Aguero has a hamstring injury and former Arsenal playmaker Nasri is suspended.
Defender Aleksandar Kolarov is back in contention but Maicon, Micah Richards and Jack Rodwell are still sidelined.
Mancini said: "We can do nothing - Yaya is in South Africa but the problem is we are missing three or four important players, Samir, Sergio and the others. But I think if we work hard we can do well."