But victory for City at Old Trafford would cut the gap to three points with United facing the tougher run-in.
"I like to play this game. I like to play at Old Trafford because it is better to win there than at home," commented Mancini.
He added: "Because when you win away in a derby it is more important for our head and our personality.
United are top but it is difficult to say who can win the title this season
Roberto Mancini
"You look at a team [United] that was winning everything and a team [City] that hasn't won anything for a long time. This can change at any moment."
Mancini believes it is now an open race for the Premier League title after a weekend that saw United lose to Wolves, Chelsea fall at home to Liverpool and Arsenal blow a four-goal lead at Newcastle, taking a point instead of three.
City maintained their momentum with a 3-0 victory against West Brom and the Italian coach is excited about what the future might hold.
"It is a derby and an important game - one team top of the table and one team third. Every game is difficult. Nobody thought United would lose against Wolves. But this is football," said the Italian.
"Now the Europa League and the Champions League start again, every week everything can change.
"Before Chelsea lost to Liverpool, I thought Chelsea could win the title. United are top but it is difficult to say who can win the title this season.
"For us it is very important for us to win something, Europa League, FA Cup, Barclays Premier League."
At United, spirits have not been dampened by the loss of their 29-match unbeaten run at Molineux, which has allowed attention to drift back towards what was always the main goal - a 19th domestic league title.
The focus has changed from that to winning the league again. That is the name of the game
Sir Alex Ferguson
"This unbeaten run was always hanging over us," said United boss Sir Alex Ferguson.
"The focus has changed from that to winning the league again. That is the name of the game.
"In normal circumstances, and it has proved itself again, you do lose games in the Premier League.
"In the run-in to the end of the season, teams will drop points. It is a fact. Whoever gets the most consistent form will win the league."
Neutral fans will doubtless hope for a repeat of the corresponding fixture last term, a seven-goal thriller settled by Michael Owen in the sixth minute of stoppage time, rather than the bore draw at Eastlands earlier this season.
There was huge hype ahead of that game in November but the build-up to Saturday's game has been relatively low-key.
"Maybe the internationals have not been a bad thing," added Ferguson.
"It has taken away a bit of focus from the game. As far as the clubs are concerned, it doesn't really matter how much hype there is. We have to perform on the pitch."
As well as the stoppage-time Owen winner, City were hit with a further two sucker-punches last season and Mancini does not want an action replay.
In the league game at Eastlands, Paul Scholes hit a late winner while Wayne Rooney followed a similar route in the Carling Cup semi-final to take United to Wembley.
"They were very lucky last year. Our team is a good team. We have improved in six months," said Mancini.
"Maybe United have a better winning mentality than us because they have won a long time. This is the only difference.
"When we start to win trophies maybe things will change. When you are winning for 20 years, your mentality is very strong.
"Also when you do not play well you know if you have a strong team at the end of the game if you do not concede a goal you can win. We have improved in this way."
Source: BBC Sport
Source: BBC Sport