Mancini still hopeful about Silva
Although Mancini has ruled Aleksandar Kolarov out of the Etihad Stadium encounter, Silva, who missed the Champions League defeat to Borussia Dortmund in midweek with a hamstring injury, remains in contention.
"We will try with David," said Mancini.
Gael Clichy and James Milner are both battling to recover from ankle and hamstring problems respectively, although Mancini is wary of pushing both men into action too quickly.
"It is a big risk because afterwards we have a lot of games between now and the end of December and we need all the players to recover."
With United boasting a three-point advantage but City having a better goal difference the two sides are in exactly the same position as they were ahead of the corresponding fixture last season.
On that occasion, City famously won through Vincent Kompany's header to seize control of the title race with just two games remaining.
There is far more football to play this time around but Mancini acknowledges the importance of the occasion.
"They can lose because they have three points more," said the City chief. "We have three points less and we can't lose."
Yet, despite his side's status as champions and the fact they completed a Premier League double over United last term, including that amazing 6-1 win at Old Trafford, Mancini insists the Red Devils are the favourites.
"They are better than us at this moment," said Mancini.
"We have only been here for two years. They are used to playing these games in the title race for 20 years. They have won everything for 15 years.
"You can't change this in two or three years. You need more time.
"For this reason they have a small advantage."