They wobbled, they teetered and for a time yesterday Manchester United looked like they were in the process of a shocking collapse. As anxiety and excruciating tension filled Old Trafford, along with the grim thought of being beaten to the Barclays Premier League title by their fiercest rivals, it was one of those moments when United’s supporters found themselves crying out to someone, anyone, in the hope of salvation.

United, with at least half a team missing, were desperate, fortunate that two goals from Cristiano Ronaldo had put them on course for the small mercy of a draw against a renascent Aston Villa. But where there is a cavalier spirit and raw enthusiasm, there is hope. And hope, then promise and finally salvation arrived in the unfamiliar shape of Federico Macheda, a 17-year-old Italian forward who was plucked from the Lazio youth team and who had never previously been involved in the first-team squad.

Whatever he may go on to achieve in the game, at United or anywhere else, Macheda will not forget yesterday. It was the stuff of fairytales, or at very least comic books. Taking a pass from Ryan Giggs, a man twice his age, in the third minute of stoppage time, he had his back to goal but controlled the ball, turned sharply and hit a right-foot shot that curled beyond the grasp of Brad Friedel and into the far corner of the net at the Stretford End, sparking the kind of celebrations that told him he had done more than just win the match.

This season is now about stopping Liverpool’s bid for a first championship in 19 years and, in doing so, equalling their record of 18 league titles — and, if Yossi Benayoun’s late winning goal against Fulham the previous day had told Liverpool’s supporters that this might be their year, that optimism was crushed by events yesterday.

Sir Alex Ferguson has seen it all in a career spanning more than half a century, but he could not contain himself at the final whistle. He strode down the touchline and punched the air once, twice, three times in front of the Stretford End.

This had been a deeply uncomfortable afternoon for the United manager, his threadbare defence brutally exposed by the aerial threat of John Carew and the pace of Gabriel Agbonlahor, but, somehow, thanks to two goals from Ronaldo and the last-gasp intervention of Macheda, they had seen off the challenge of Villa and, in doing so, had changed the mood from one of despair to one of euphoria.

United have some tricky fixtures remaining, but it is hard to imagine that they will endure many more testing assignments than this. Villa, without a win in their previous eight games, travelled north low on confidence, but they could not fail to be invigorated by the teamsheet, which revealed that United had at least five first-choice players missing, with Rio Ferdinand’s groin injury, combined with Nemanja Vidic’s suspension, meaning that Gary Neville, who had not played since January 31, was forced to partner the inexperienced Jonny Evans at centre half.

Ferguson called that a gamble but it was one that backfired, as he belatedly acknowledged by swapping Neville with John O’Shea. At one point Neville raced 20 yards to hit Agbonlahor with a hard but fair challenge, but that was an isolated highlight in a grim opening half-hour for the 34-year-old club captain.

Whether he was being taken on by a resurgent Agbonlahor or beaten in the air by Carew, Neville looked like a fish out of water. Finally, after a series of near-misses, Gareth Barry crossed from the right and Carew rose above Neville to beat Edwin van der Sar with a firm header on the half-hour.

United had taken a fourteenth-minute lead when Ronaldo placed an indirect free kick into the top corner after Friedel, under pressure, picked up an ill-advised back-pass from James Milner, but their first-half performance was every bit as disjointed as Ferguson might have feared in the absence of Dimitar Berbatov and Wayne Rooney. Ronaldo, his goals aside, was having one of those days where he looks like he is saving himself for Real Madrid, while Nani, once his heir apparent, plumbed new depths in what has been a bitterly disappointing campaign.

By the time Nani made way for Macheda, United were behind. Ronaldo lost the ball cheaply and Villa counter-attacked at speed down the left. It was Carew who carried the ball forward, with Agbonlahor waiting in the middle, but the outcome was what every Villa — and indeed Liverpool — supporter wanted, the Norwegian’s cross headed in powerfully and bravely by the young England forward, his first goal in nine games.

For a time, United looked helpless, barely even threatening in the 20 minutes that ensued, but suddenly, from nothing, they found a foothold, Michael Carrick teeing up Ronaldo for a left-foot shot that sneaked inside the far post from the edge of the penalty area.

With that, the atmosphere changed. Suddenly United had the whiff of glory in their nostrils and, with a couple of teenagers leading the line, they went for it. Finally, in the third minute of stoppage time, they claimed their reward. And if they can win while playing like this, with half a team missing, there is only one name on this Premier League trophy — and it is not Liverpool.

Manchester United (4-4-2): E van der Sar 7 - J O’Shea 5, G Neville 4, J Evans 5, P Evra 4 - C Ronaldo 7, D Fletcher 7, M Carrick 5, Nani 3 - R Giggs 5, C Tévez 5. Substitutes: F Macheda 7 (for Nani, 61min), D Welbeck (for Tévez, 88). Not used: B Foster, R Eckersley, D Gibson, Park Ji Sung, L Martin. Next: Sunderland (a).

Aston Villa (4-4-2): B Friedel 6 - L Young 5, C Davies 5, C Cuéllar 6, N Shorey 5 - J Milner 6, S Petrov 6, G Barry 7, A Young 6 - J Carew 7, G Agbonlahor 8. Substitutes: N Reo-Coker (for Milner, 76min). Not used: B Guzan, Z Knight, C Gardner, M Salifou, M Albrighton, N Delfouneso. Next: Everton (h).

Referee: M Riley Attendance: 75,409

Porto stretched their unbeaten league run to 16 games by beating Guimarães 3-1 on Saturday. The Portuguese league leaders, who face Manchester United in the Champions League at Old Trafford tomorrow evening, went behind in the nineteenth minute but recovered thanks to goals by Ernesto Farias, Mariano González and Rolando as Jesualdo Ferreira’s team stayed on course for their fourth consecutive title. Hulk, the Brazil forward who is expected to leave the club this summer, was the man of the match.