It seemed that Paul Scholes had won the game for a makeshift United, missing half of their regular first team, when he dived to head home Eric Cantona's cross but gutsy Wimbledon, who might even have won the game had they been more ruthless, responded immediately when Robbie Earle headed home Alan Kimble's free-kick.
The last time United had lost an FA Cup tie was in the final of 1995 against Everton, their only defeat in the competition, in fact, for four years. Yesterday's team, however, was a shadow of the potent force that has dominated the competition in the Nineties.
Injuries to David May, Ronnie Johnsen and Gary Pallister meant that Alex Ferguson fielded a defence comprising two FA Cup debutants in the 19-year- old Michael Clegg and 21-year-old Chris Casper, with Roy Keane lining up in the middle of a back five. In addition, David Beckham was missing while Andy Cole and Ole-Gunnar Solskjaer were only substitutes, Eric Cantona the spearhead.
Suddenly Wimbledon, beaten 3-0 at home by United on opening day, would have fancied the task even more. Though recent defeats at Aston Villa and Leicester have interrupted their Premiership momentum, their progress to the semi-finals of the Coca-Cola Cup testifies to their doughty cup character.
United's aim seemed to be to draw Wimbledon forward and strike on the counter-attack, through the wide men Karel Poborsky and Ryan Giggs. As much was seen when Wimbledon were caught out by a neat one-two between Cantona and Giggs, the latter's cut-back from the byline being blazed over the bar from six yards by Keane, who despite the piece of wasteful finishing was beginning to stride forward confidently.
It was, however, a rare United attack amid Wimbledon's pressure as they clearly felt the game to be within their grasp. They should have had the lead when Earle's cross dropped invitingly for Marcus Gayle but he sliced his volley wide. Soon after, Dean Blackwell almost bundled home Vinnie Jones's cross.
Keane was being forced into a towering performance at the back for United, though yet again he undermined his work for a yellow card after a lunge at Oyvind Leonhardsen. He had some help from the hard-worked Peter Schmeichel, who dived to save a low shot from Efan Ekoku after Neil Ardley's corner had reached him.
For all their dominance, however, they continued to look vulnerable when United broke and Neil Sullivan, contentiously, was adjudged to have brought down Poborsky on the edge of the Wimbledon penalty area as they chased Brian McClair's through ball. From Giggs's curling free-kick, the goalkeeper atoned with a splendid save, however, repeating it moments later as United sustained a spell of pressure.
The pattern continued after half-time with United now looking more assured as they sought to increase the tempo of the game. Perhaps they, too, sensed that Wimbledon, having failed to take advantage of the patchwork nature of the home side, were beginning to entertain self-doubt when they should have been more ambitious in seeking a goal.
Cantona's ball infield found Keane again surging forward past Jones and though his shot was sliced wide, it was more like the United all have come to fear. An end to the deadlock also looked feasible when Cantona chased a through-ball by Giggs, whose influence was growing, only to fall under challenge from Kimble. The referee, Graham Poll, was unimpressed, booking Cantona for diving, indeed.
Now Wimbledon sought respite in the counter-attack and they looked sure to score when Gayle raced clear. Ekoku could not quite reach his low cross and another chance went begging.