That is not to detract from Sunderland, whose response to a run of four Premiership defeats was to produce a performance which was urgent, committed and deserving of their first victory for two months. But they were playing a team whose emotionally draining exploits of three days previously had left them in no condition to get down to the business of nicking points off relegation candidates. The only resemblance between this Manchester United and stirring deeds against Portuguese opposition was an all-blue strip reminiscent of the one they wore the night they beat Benfica at Wembley in 1968.
It was a match United simply did not want to know about, and probably will not dwell on. "We were knackered," said Alex Ferguson. "We'd shot our bolt." Criticism of them seems superfluous in the light of the football they played against Porto. But the consequences of the result, their first defeat since losing at home to Chelsea in November, may not be so easy for them to ignore. With Arsenal beating Nottingham Forest, United's lead at the top of the Premiership does not look unassailable, and should Newcastle win at Liverpool tomorrow night, it would be back to a four-way contest for the title.
European games take so much out of United that they become a liability to themselves the next time they take the field. Of the matches that have followed their past five European outings, they have lost three and drawn two. If the pattern continues, they could struggle at Everton, which comes after the away leg against Porto, and at Blackburn, where they must go following the first leg of the European Cup semi-final on 9 April - always assuming United are in it. The second leg of the semi-final, on 23 April, is followed by a blank weekend in the Premiership, and that could be crucial for United.
Where there was no excuse for United falling short was in the contribution of the three men Alex Ferguson brought in who had not played against Porto - Brian McClair, Karel Poborsky and Jordi Cruyff. Ferguson said he did not think Andy Cole and Ole Gunnar Solskjaer "would have given us anything anyway", so exhausted were they, and Ryan Giggs's absence was confirmed when he strained a hamstring in the warm-up. But their replacements hardly figured as Sunderland took the game to United, and in the end Cole and Solskjaer came on just before the hour. But by then United were a goal down and the cause was beginning to look lost.
This was Peter Reid's first victory as a manager over United, and it went some of the way to making up for Sunderland losing to them in an FA Cup replay last season - after his team had outplayed them for much of the first match - and the 5-0 defeat they suffered at Old Trafford earlier this season. It also produced one of the last of the Roker roars, with only four matches left at the ground before Sunderland move to their new stadium next season.
Reid praised his front pair of Michael Bridges and John Mullin, whose running and linking play disconcerted a United defence that was missing Gary Pallister with a groin injury and had to be reorganised, with Ronnie Johnsen coming into a back three with David May and Denis Irwin, and Gary and Phil Neville playing as wing-backs.
It was Mullin's challenge for a cross from Gareth Hall that forced Peter Schmeichel into an error and gave Michael Gray the chance to put Sunderland into a 57th-minute lead. Mullin scored the second 14 minutes from the end when he broke upfield and Schmeichel could only half-stop his shot. Even though Andy Melville's own goal a couple of minutes later meant Sunderland suffered some anxiety over the closing stages, United never seriously threatened.
Goals: Gray 57 (1-0); Mullin 76 (2-0); Melville 78 (og, 2-1).
Sunderland ((4-4-2): Perez; Hall, Melville, Ord, Kubicki; Kelly, Ball, Bracewell (Williams, 84), Gray; Mullin, Bridges (Russell, 74). Substitutes not used: Preece, Howey, Eriksson.
Manchester United (5-4-1): Schmeichel; G Neville, Johnsen, May, Irwin, P Neville; Poborsky (Solskjaer, 57), Beckham, McClair, Cantona; Cruyff (Cole, 57). Substitutes not used: Giggs, Van der Gouw, Casper.
Bookings: Sunderland Mullin, Ord.
Referee: P Jones (Loughborough).
Man of the match: Mullin. Attendance: 22,225.