Mancini started with the same team that beat Wolves 2-0 last week, with Zabaleta selected ahead of Micah Richards at right back, Toure and Barry playing as the deepest midfielders and Silva, Nasri, Tevez and Aguero starting in an offensive-looking team for City.
Meanwhile Ferguson started with Smalling at centre back, Carrick and Scholes playing in the centre, with Giggs and Nani in the wide areas and Park looking to support Rooney through the middle.
United started the game pressing high and compact, trying to stop City from passing through midfield and hoping to regain and counter attack. Park, playing in the middle, was helping Carrick and Scholes when City had possession and then pushed high when United regained the ball. Both Giggs and Nani were moving inside which created space for both the full backs to get forward in the wide areas while Rooney dropped deep.
This intensity from United didn't last though and after a while, they began to drop off while City dominated possession. After 22 minutes they had had 61% of the ball.
David Silva was moving inside from the left, trying to receive passes between the lines from Toure and Barry and also looking for the second ball when City went long for Aguero. However they were having problems to penetrate because of United's bodies in the middle, the first chance for City being created after Nasri went past two United players outside the area and played Tevez in, aside from the centre back.
One of the things City were looking to do was to stop Scholes and Carrick dominating the play when United got possession, so they initially looked to press high with their front four, full backs and Toure and Barry in the middle, while they left Park to the centre backs. This helped limit United's transitions; the away side were trying to counter attack from deep with the first pass to Rooney and then looking to move the ball to the wide areas but they were either too slow or too quick and they didn't create any clear chances on the counter attack.
In the last twenty minutes of the half, City began to look more threatening. Zabaleta and Clichy moved high, allowing them to switch the play to stretch United laterally, and they were then able to find spaces with passes from out-to-in, helped by good speed in possession. Giggs was tucked in narrow on the left which allowed Zabaleta more space and time on the ball to play a pass on the right. With United dropping deeper, the home side created a couple of good situations when they got high in the wide areas and then sent low crosses into the area for lay offs or pull-backs.
However it was a corner, something with which City had had problems themselves in the first half, where they got their goal. Kompany, man-marked by Smalling, managed to find space, losing the United defender and heading in to make it 1-0 at half time.
City came out with a different game plan in the second half, with more concentration on defending their lead, with their midfield dropping off more and looking to counter. Both teams were slightly more open, even though there were not many clear chances. United were getting more of the possession but were unable to penetrate City, with Mancini's men defending well down the middle and Ferguson's men too slow to penetrate out wide, allowing City to double up if they needed to. United's biggest threat was from set pieces but even then they couldn't create a clear chance.
Ferguson brought Welbeck on for Park in the 58th minute, changing the system to two strikers, though with Rooney dropping deeper and United looking to threaten more down the middle with passes to both him and Welbeck between the lines. However City's centre backs' anticipation and strength made it difficult for United to turn and face Joe Hart's goal and their two lines of four were very organised and compact. Carlos Tevez, still playing high up, was also closing down so as to slow United down in possession and make it easier for City to press.
Mancini's substitution of De Jong for Tevez helped City's defence down the middle which in turn allowed Yaya Toure to play higher up and use his pace and physical power between United's midfield and defence. The Ivorian had two chances to make it 2-0 with two shots from just outside the area that went wide after he had found space on the counter attack
In fact, though United were losing, it was still City who looked the most like scoring. Valencia and Young came on for United to try and provide more penetration in the wide areas but there were very few 1v1 situations and when there was, it was for Jones, the right back, who badly overhit his cross.
Mancini brought on Micah Richards for David Silva with eight minutes of normal time to go, which meant City reverted to a five-man defence, with Barry and De Jong in front, allowing Toure, Nasri and Aguero the freedom on the counter attack and Nasri probably should have finished it off with a chance just into stoppage time.
United's transitions were still too slow and with at least seven men to get through at all times they found it very hard to penetrate, even though City were often dropping very deep. And with not a single shot on target for the whole game, United clearly didn't do enough to get anything.
City were definitely the better side for most of the game. United's transitions were poor throughout and they were unable to force Joe Hart to make a save. A game not so much about systems but more about the carrying out of the systems and City were in control for most of the game. The title race now gets even more interesting with two games to go.