Arsenal had two pre-match observations to take some motivation from: Patrice Evra's claim that they are a "training ground team" who will win "no trophy, nothing", and Sir Alex Ferguson's claim in last night's programme notes that they are not as "lilywhite" as they seem. It was easy to imagine when Evra made his comments on Canal+ last week that Ferguson would have been irritated at the unnecessary source of inspiration but as Arsène Wenger's side went about their work you sensed that it had provoked rather than primed them.
Arsenal's football in the first half was not quite the "anti-football" that Wenger described at this stadium two years ago, but the sight of Andrei Arshavin ploughing through Darren Fletcher, Jack Wilshere squaring up to the same player and Marouane Chamakh upending Nani, suggested a case of Evra's comments going to their heads.
It was in that chaotic and intemperate phase of play that Fletcher calmly climbed to intercept and head on the ball which set in train United's goal – Rooney sending it on to Nani whose spinning cross was headed home by Park Ji-Sung on the same arced trajectory.
A less temperate player than Fletcher would not have been composed to make that critical header, given that Wilshere had only just finished squaring up to him, but Fletcher was only proving his assertions of the past week – that there is a difference between malice and determination. "I am not a dirty player. I go to win the ball and sometimes you give away fouls doing that but it's not malicious or dirty and it's all part of the British game," he said a few a days ago. Wenger's barb seemed to have cut him deeper than we thought.
His contribution thereafter was equally unlaboured – a foot in here, a tackle there – but by the midpoint of the second half when Anderson was picking off possession from Wilshere in front of the Arsenal box and sprinting into a counter-attack, the contrast between the two midfielders was unmistakable.
Opposition players sense a weakness like Wilshere's and in the next phase of play Fletcher pounced on him as he dawdled in possession. The dot matrix board was raised soon afterwards and the Englishman was on his way to the touchline. Taken with his removal at half-time at Goodison last month, Wilshere looks like a player under development. It has been a season of indifference for him at times and even Anderson had much more to take away from last night than him.
It was no more a vintage display from United than a perfect match which suggested either side will stride away to the title. Perhaps it was the sense that, with Chelsea faltering, that this fixture means so much that gave it a more ill-tempered and untidy complexion than many between these two.
Nani was an epitome of the frustration from a United perspective, tormenting Gaël Clichy in the first half before spinning the vital cross off the defender's boot for Park to twist in with his head. Yet the way he wasted that breakaway move Anderson created was a scandal. First, Nani was dispossessed in his exuberance, and then, having won back the ball and then raced in again, he blasted high and wide – indifferent to the awaiting, infuriated Rooney.
But their degree of comfort – Edwin van der Sar was not troubled – gives United reason to believe that they can process onwards towards the title, with that unbeaten record increasingly becoming a source of psychological strength. The draws which plagued United earlier this season seemed like an impediment to their progress at the time. Now we remember that Arsenal drew 12 games en route to their title as "Invincibles", their combination of flair and steel proving decisive. United are beginning to become intrigued by the idea of going all season undefeated – "an interesting challenge" is how Fletcher has described it.
Fletcher also expected more from this opposition. "The physical presence of Alex Song in midfield, the aerial prowess and physicality of Chamakh definitely helps them," he said last week. Little did he imagine that when it came down to it, that physicality would prove a hindrance.
Man for man
Edwin van der Sar: Veteran had little to do in the first half and dealt well with what was thrown at him. 6
Rafael da Silva: Got forward at every chance, including one fine dribble into Arsenal area. 6
Rio Ferdinand: Recovered from hamstring injury to add a reassuring presence to back line. 7
Nemanja Vidic: Continued his fine season, snuffing out danger and posing a threat at set pieces. 8
Patrice Evra: Target of chants from the away fans. Forced to focus on defensive duties. 6
Darren Fletcher: Hard-working as always, mopped up at the back and kept attacks moving. 7
Michael Carrick: Responsible for breakdown of one attack with a poor choice of pass. 6
Anderson: Buzzed around, but not always to great effect. Enjoyed battle with Clichy. 7
Nani: Screwed one half-volley just wide but generally United's best attacking player. 7
Park Ji-sung: Adapted superbly well to guide Nani's cross inside the far post for only goal. 7
Wayne Rooney: Continues to persevere as he searches for return to form. Awful spot-kick. 7
R Giggs (for Anderson, 85) Provided an experienced head for final minutes 6
Wojciech Szczesny: Confident display on league debut, making some important saves. 7
Bacary Sagna: Advanced at will when the visitors were in possession but erratic crossing. 6
Sébastien Squillaci: Less convincing than his fellow centre-back but stood up well to the test. 5
Laurent Koscielny: Made a number of key interceptions to keep Gunners in contention to the end. 6
Gaël Clichy: Mistake let in Nani for chance and gave away penalty to the same player. 5
Alexandre Song: Mixed performance. Sloppy in possession early on but a strong presence. 6
Tomas Rosicky: Shot across face of Van der Sar's goal after one promising move. Ineffective. 5
Jack Wilshere: Struggled at times but feisty, and creative when given time on the ball. 6
Samir Nasri: Continued recent form. Had free reign of midfield at times but limited effect. 7
Marouane Chamakh: Got very little out of Ferdinand and Vidic, and fluffed his one good chance. 6
Andrei Arshavin: Not one of his better displays. Unsure of best pass and ran into blind alleys. 5
Fabregas (for Rosicky) 6; Van Persie (for Wilshere) 5; Walcott (for Arshavin) 6.