Not so much a dead rubber as an energetically zombified title decider-that-might-have-been, this was a game given life by its own big city derby verve; and beyond that as a kind of self-contained minority report, a story of the season that might have been as Manchester City's awakening midfield provided the driving force behind a deserved 2-1 victory at Old Trafford. City played like champions in snatches here, whereas United, who will soon in spite of it all be champions again, played like the tired, spirited but creatively limited team of the last three weeks.

In many way it was also a rather pointed tale of two strikers: Sergio Agüero's winning goal was sublime, a scrambling solo run across the penalty area followed by a momentum-defying reversed right footed finish. And yet for all the glory of the moment Agüero has been one of those culpable in City's minor but telling sense of drift: this was only his third goal in the Premier League this year and his third all season against teams in the top half of the table, a paltry return for a grand-scale talent.

For United Robin van Persie provided a snapshot both of his own oddly dwindling season in front of goal and also of where Sir Alex Ferguson will surely look to recondition this still transitional champion-elect team. It was fitting that it should be Van Persie, deprived of clear attacking air near goal by a prosaic United midfield, who provided the moment of incision that brought the equalising goal after 58 minutes, levelling James Milner's opener. His driven free-kick was malevolently inviting, the deflection off Vincent Kompany's head not so much unfortunate as unavoidable. The Dutchman celebrated like a goalscorer — but then he has not had the chance to do that much of late.

It always seemed likely Van Persie would have some kind of say here and in the event he was easily United's most enterprising attacker, producing some wonderful, and often unappreciated movement and justifying Roberto Mancini's slightly odd fixation before the match with his own club's failed attempts to sign the Premier League's second top scorer. But then Van Persie has been a puzzling figure all round of late. Ferguson has suggested fatigue might be the cause of his recent tailing off in front of goal but the evidence suggests United's forward rapier may be suffering as a result of deeper structural problems. He played here in his self-coined nine-and-a-half role, a position that showcases his exceptional movement 30 yards from goal, a darting intelligence that was in evidence throughout and which, along with three goals in two games for Holland in the international break, does not immediately suggest a star player with a clouded mind.

Van Persie's name drew the loudest cheer before kick off at a boisterous Old Trafford illuminated by powder blue evening skies for the first time this season. Playing up front ahead of the energetic but peripheral Wayne Rooney, Van Persie's scholarly movement was in evidence as early as the sixth minute as a twirl and sprint took him into space for a lofted pass from Ashley Young. Moments later he conjured up a genuine rarity, a kind of shrugging full-body swerve 20 yards from the ball that sent Kompany the wrong way and allowed Rooney to play a cute ball into his path. The shot was rolled just wide of the far post but it would have been a lovely self-penned striker's goal.

Throughout the first half the contrast with City's own lone frontman was pronounced. Where Van Persie has an equine elegance in his movements, at his best Carlos Tevez — damned indirectly by Mancini's pining after his opposite number — scuttles like a ravenous scullery mouse. He was increasingly prominent as City's midfield began to shade possession, with David Silva twinkling at times in the way David Silva used to twinkle, a darting presence between the lines of attack and midfield, and Milner providing persistence on the right.

At the other end United's chief attacking threat was turning in a performance characteristic of his season since Christmas: decorated with quick-feet link-up play but still without a goal, or even any clear chance of scoring one as United's midfield looked spirited and technically neat but lacking in any telling creative qualities.

Even as United have taken incremental strides towards a 20th title this year, Van Persie's accompanying goal drought surely has something to do with this absence of coherent supporting expertise. As they had been against both Chelsea and Real Madrid, United were out-passed and outmanoeuvred in midfield here. Even the slightly fortunate move that brought City's opening goal was an extension of their willingness to attack in numbers, the ball funnelled to Milner via a deflection after Ryan Giggs conceded possession. Defensive resilience, the craft of Michael Carrick and Van Persie's ruthlessness in early season may have taken United this far but the Dutchman's barren spell does not exist in isolation.

United will build from a position of strength again in the coming months. One lesson here, beyond a glimpse of City's own latent champion quality, is of the likely shared forward benefits of a little high-class midfield reinforcement.