Champions City have won the last four league meetings against United, including a 1-0 victory at the Etihad Stadium in November, but their hopes of retaining the title have faded.
They have dropped down to fourth after four wins in 11 league games and trail leaders Chelsea by nine points.
United, meanwhile, have put their early season struggles behind them to climb to third, eight points clear of fifth-placed Liverpool in the race for Champions League qualification.
“It was another Manchester United (last November), I believe,” United boss Louis van Gaal told reporters after Saturday's 3-1 win against Aston Villa.
“That was more in the start of the process and now we are in the end of the process.
“Now we have developed the team. I think also the confidence of our players is very high at the moment.
“This next game is the decisive game... you have to win these kinds of matches.”
City arrive at Old Trafford on the back of a 2-1 defeat by Crystal Palace but captain Vincent Kompany believes form counts for nothing in a derby.
“It doesn't matter what place you are in the league, it's a derby,” Kompany said after the Palace loss.
“If anything, it's a good moment to go into a derby.
“I guess the momentum is a little bit with our neighbours at the moment, but it's the perfect place for us to go and try to rectify what we've had.”
Chelsea, who need 16 points from their remaining eight games to win the title for the first time since 2010, travel to relegation-threatened west London rivals Queens Park Rangers on Sunday.
“I've never played at QPR as a Chelsea manager,” Jose Mourinho told the club's website (www.chelseafc.com). “But I know history and I know that for QPR to play against Chelsea is a special match.
“The most difficult job is the job of the others that come from behind, because... if they draw one game, they are in trouble. They have to win every game.”
Second-placed Arsenal, who have won 10 out of 11 league matches, travel to struggling Burnley on Saturday, while fifth-placed Liverpool will be aiming to close the gap on the top four with victory over Newcastle United at Anfield on Monday. – Reuters
Original source: United take aim at ailing City