Arsenal have overcome Manchester United at last, just when it seemed that the reliability of Sir Alex Ferguson's side was beyond dispute. They had not been beaten by the Gunners in a span of seven games, spread over two-and-a-half years in all competitions. United have now faltered just when a great deal is at stake. The lead over Chelsea in the Premier League is down to three points because of Aaron Ramsey's goal.

For the first time, the manager and players must sense jeopardy on this front. They will, indeed, be particularly glad now of the 2-0 victory against Schalke in Gelsenkirchen that relieves the return in the Champions League semi-final on Wednesday of nearly all of its strain. Energy and concentration should be conserved for the arrival at Old Trafford next Sunday of Chelsea, who will head the table on goal difference if they can win there.The prizes are still within reach of United, even if the anticipated Champions League final with Barcelona at Wembley will be a severe challenge.

There has been a temptation all season to regard Ferguson's line‑up as a diminished version of those he has sent out in days gone by. Results in Europe do not endorse that verdict, but on the domestic front the faltering displays in away games are undeniable. On their Premier League travels, they have taken 24 of a possible 54 points.

Contrary to caricature, Arsenal have been much more robust in the away matches. Indeed, United have been outscored by them 36 to 28 on that front. Observers might be tempted to ask how Arsène Wenger's men have contrived not to be in hot pursuit of the title. That is an academic issue for United, who can be glad at least that their concern, primarily, is with Chelsea alone. If Ferguson is uneasy, it will be because his line-up achieved so little at the Emirates. Arsenal seldom keep a clean sheet against United.

They could have failed to do so again but the referee, Chris Foy, gave no penalty near the end when Gaël Clichy's studs went into the calf of the substitute Michael Owen near the end. Even so, it is a small indictment of United that openings were scarce. Arsenal, on the face of it, were not formidable in defence. When an injured Johan Djourou went off there was no alternative but to send out Sébastien Squillaci from the bench, but the opposition still failed to whip up panic.

They had no answer to a goal from a player whose impact would be appreciated by anyone without a vested interest in success for United. Ramsey, in his low moments, may have felt he had been sent into exile during the loan spells at Nottingham Forest and Cardiff City that came after he was striving to recover fully from a broken leg. There might not have been any part for him at all against United had Cesc Fábregas not been ruled out by a thigh strain.

Rather than mope, Arsenal reacted with enough boldness to prevail. There was much to exasperate them and United were not alone in having penalty appeals spurned. Wenger's men ought to have been given the opportunity to open the scoring 12 minutes from the interval. Nemanja Vidic had an arm extended and made contact with a cross from Theo Walcott but Foy, averse to pointing to the spot in this match, took no action.

There was a muddled tone to events in this encounter. It was a windy afternoon and other factors also made it difficult for players to show poise. United were naturally combative, with Anderson initially making his presence felt at the core of midfield.

Foy gave a minimalist performance and declined to award a free-kick earlier, when Vidic seemed to foul the influential Jack Wilshere near the penalty area. Despite such incidents, the visitors usually looked sound, even if they were eventually to succumb.

As if it was not hindrance enough for Arsenal to be denied the presence of Fábregas, Samir Nasri could not continue beyond the interval because of a hamstring problem. Nonetheless, it was United who suffered. Ferguson must have anticipated taking command as they have done in the past at the Emirates, and the Arsenal goalkeeper Wojciech Szczesny did make a good save from a Wayne Rooney free-kick soon after the interval. Even so, Arsenal had started to impose a pattern in their build-up and settled the match after 56 minutes.

Ramsey slipped a low ball from Robin van Persie into the corner of the net. This was only a second start for the scorer in their league campaign. United, however, could be excused for lacking any glow of benevolence towards a player striving to regain his career in the top flight.

Just before the goal the visitors had brought on Antonio Valencia, as if they expected to be on the attack. Once Arsenal were in front adventure was obligatory but Wenger's men coped well enough with Szczesny, for instance, blocking a shot from an angle by Nani. For the moment at least, there is an obstacle, too, in United's path to the title.