Would you give a new long-term contract to a player still on crutches after suffering, with a double fracture to the tibia and fibula of his lower right leg, an injury that has ended careers? Arsène Wenger did, on 1 June last year, and on Sunday Aaron Ramsey repaid his faith, scoring the goal that puts life back into the Premier League title race while showing Arsenal that they are still capable of winning a high‑pressure game.

Ramsey was playing because Cesc Fábregas had suffered a blow on his thigh in training. The 20-year-old Welshman has been working his way steadily back towards the first team since playing his first match for the reserves last November, nine months after his bones snapped under the impact of a reckless challenge by Ryan Shawcross of Stoke City. As part of his rehabilitation he was sent out on loan, first to Nottingham Forest and then to his old club, Cardiff City, before being recalled at the end of January. He made his first appearance from the bench against Manchester United in the FA Cup on 12 March, and a week later he was in the starting line‑up against West Bromwich Albion.

His second start came here in this game, in one of the most important matches, in psychological terms, of Arsenal's season. Having seen their challenge on three fronts crumble in the space of a fortnight with defeats by Birmingham City in the League Cup, Barcelona in the Champions League and Manchester United in the FA Cup, another reverse against United would have extinguished their slender hopes in the Premier League. The loss of Fábregas on the eve of the match was hardly the most helpful of omens.

Before his dreadful injury, Ramsey was looking like a replacement for the Spaniard, showing himself to be on the brink of becoming the captain's equal in terms of mobility, tactical awareness and deft passing. His leadership qualities had also been in evidence, notably with Wales's Under-21 squad, while his full international debut at 17 made it seem as though he had the potential to become his country's finest all-round footballer since John Charles. All of this could have been swept away by Shawcross's impetuous lunge.

Against United here Ramsey lined up alongside Jack Wilshere in central midfield, in front of Alex Song and behind the front three. It was always going to be interesting to see how the Anglo-Welsh partnership functioned as the youthful engine room of a sometimes misfiring team, and their neatness and persistence were at the heart of Arsenal's early dominance.

But how many times have we witnessed Wenger's current squad begin a match with a flood of precise short-passing approach work, only to see a majority share of possession and pressure avail them nothing? All it takes on such occasions is a couple of offside decisions and a handful of wastefully misplaced passes, and the air starts to leak out of the balloon. That was the feeling among the home fans at half‑time, with the added pain of the refusal of a clear penalty when Nemanja Vidic used his hand to deflect Theo Walcott's cross away from the head of Robin van Persie.

Ramsey had begun that move, in just one of several constructive interventions during the first 45 minutes. Only the occasional over-elaboration in his exchanges with Wilshere, and a weak shot from a promising position just outside the United area, spoiled the good impression made by a player whose graceful, economical movement and general alertness make him a pleasure to watch.

At the start of the second half Arsenal's supporters were nursing the fear that they had seen this movie before, and United were doing most of the attacking when Sir Alex Ferguson, having shown signs of displeasure with Anderson, replaced the Brazilian with Antonio Valencia. Thirty seconds after the switch, while Park Ji-sung was adjusting to his new role in the centre of midfield, Ramsey's moment arrived.

With the ball at his feet just inside the United half, he made a handful of yards before measuring a pass to Van Persie on the right. While the Dutchman was forcing Patrice Evra to back off on the edge of the penalty area and manoeuvring the ball on to his left foot, Ramsey ran on to meet the careful return with an accurate right-footed shot inside the left-hand post.

His success condemned Arsenal to endure a final half-hour of pressure from the visitors, who were keen not to become the fourth of this year's Champions League semi-finalists to lose over the weekend. Ramsey shouldered his share of the defensive burden, although by bringing down Park, blocking Michael Carrick's cross with his arm and taking Rooney's legs at the same time as the ball in the fourth minute of injury time, each offence committed just outside the Arsenal area, he also succeeded in adding to the suspense. On balance, however, Wenger will feel that the day gave him not just three points and a welcome boost to the squad's morale but the restoration of a player who can play an important part in the club's future.