Tonight's match at the Etihad Stadium has been billed as unmissable, and with good reason. Both clubs go into the game with the knowledge that a victory takes them within touching distance of a historic trophy.
For Manchester City it would mean a first title since 1968. For United, it would be the 20th league trophy in an unprecedented period of success in the club's history.
Each side will be desperate to secure a win that would put them within two games of the title. City began the season in irrepressible form, dispatching all comers as they blazed a trail at the top of the league.
However, United have fought back in typical style, surging five points clear in early April before a recent stumble cut their lead back to three points. If previous meetings between the sides are anything the go by tonight's match should be a classic. Manchester derbies are always highly anticipated and fiercely competitive but never has so much been riding on one's outcome.
Both side's will have done their homework and United will be especially keen to banish the memory of their humiliating 6-1 defeat at Old Trafford earlier in the season. For them to achieve that goal, however, Sir Alex Ferguson and United will need to be at the top of their game.
It promises to be a tight affair and with that in mind, a few areas could be crucial in deciding the outcome.
City are especially strong through the middle, with Yaya Toure and Gareth Barry impressing this season in a City side that likes to control possession. In contrast, United have struggled at times to dominate games in their usual manner - last weekend's draw with Everton was a prime example.
The return of Paul Scholes has alleviated this concern to a certain extent but City will still feel they have an advantage in this key area of the pitch. Scholes made his comeback against City in the FA Cup match in January, with United running out 3-2 winners at the Etihad. His 96 percent pass completion rate that day was a sign of things to come and the former-England midfielder's return proved a huge boost for the United midfield. Tonight, Ferguson will most likely drop Wayne Rooney off the front to help out and the England forward will be crucial if United are to keep hold of the ball.
City's pair of Toure and Barry have formed an effective defensive shield at City, allowing Gael Clichy and Pablo Zabaleta to bomb forward. Their position sense has been good all season and could be key tonight, as United's biggest threat is likely to come from out wide.
While central midfield may pose a few problems for the Red Devils, out wide they possess pace and trickery in abundance. Antonio Valencia is certain to start on the right, and whether it be Nani or Ashley Young on the left, either has the ability to hurt City's full backs. In the past Ferguson has opted for Park Ji-Sung in the big games but to play the Korean in this tie would be a negative move. City's full-backs enjoy the freedom to contribute in forward areas and United should exploit the space in the channels.
Spreading the play early and often will be important for United as they look to keep the play away from the congestion in the middle of the park. While City's width is often provided by overlapping full-backs, with David Silva and Samir Nasri prone to cut inside, United possess genuine wide players. Good quality service into the box could be the difference between victory and defeat for United.
Manchester City's summer spending spree means that Roberto Mancini enjoys the luxury of a deep bench. As a result he has plenty of options should the tie not be going his way.
Edin Dzeko and Mario Balotelli are likely to start on the sidelines, giving the City boss the ability to respond quickly if United take an early lead. United's reserves are a little more stretched. Rooney and Danny Welbeck should start, leaving Javier Hernandez as Ferguson's only real forward option.
Although this season's top four encounters have proved to be goal-fests, the importance of this occasion should temper each side's attacking instincts. An early goal could change all this, however and you feel United will look to keep it level for as long as possible, with a view to nicking a goal in the second-half.
If that's the case, tactical changes for both teams could be the difference.
City may have more quality on the bench but United possess the experience. Ryan Giggs and Scholes have 22 Premier League winners medals between them and that little bit of know-how could give United the edge.
In contrast, Kolo Toure, Gael Clichy and Carlos Tevez are the only players to have tasted Premier League success in the Etihad side. If City get it right tonight it could lead to the first of many, get it wrong and United will relish this 20th title as one of their best ever.
The performance of each side's key players will be crucial tonight and for both teams the potential match-winners occupy forward roles. For United, an on-form Rooney could carry his side to victory, or even the crucial point that would keep City at bay and keep United in the driving seat. The England striker will be tasked with dropping back to assist the midfield this evening but his work going forward will be key.
His link-up play with Welbeck has been promising, and was exceptional for much of the Everton game and the two should reprise their roles tonight if United are serious about taking all three points. Rooney's 34 goals have largely carried United this season - their next highest scorers are Welbeck and Hernandez with 12 - but the return of the Lescott-Kompany partnership has sured up the City defence.
In contrast, United shipped four at home to Everton last weekend. Rio Ferdinand and Jonny Evans had been enjoying a fantastic second-half of the season until that result and they will need a sharp return to form if they are to keep Sergio Aguero quiet.
The Argentinian double-act with Tevez has proved prolific through April and Silva seems to have rediscovered his midas touch just in time for the title chase. The Spanish maestro pulled the strings at Old Trafford earlier this season and Mancini will hope he can once agin create plenty of openings for the City strikers.
If it does prove to be a cagey affair, one moment of magic from these match-winners could secure their side the title.