So much went wrong here for Manchester United last night that the first sensation their players may encounter as they awake this morning is relief that their dreams of a treble remain alive.

Such equanimity is unlikely to fill the minds of the club’s supporters, after they became the latest English fans to be subjected to brutal treatment by the Roman police, but this was such an uncomfortable evening at times that things could have been even worse.

As with United’s tie away to Lille in the previous round, this was a match overshadowed by ugly scenes in the stands and, as on that occasion, Uefa is likely to censure both clubs. But Sir Alex Ferguson is likely to concentrate more on what had happened on the pitch. His team, who lost Paul Scholes to a red card in the first half, were over-run at times by an AS Roma side built around the talismanic talents of Francesco Totti, and it took a display of considerable character to emerge with only a 2-1 deficit.

Ferguson called it a “creditable result”, revelling in the goal scored by Wayne Rooney, but Roma showed enough quality to suggest that they could go through after the second leg at Old Trafford on Tuesday.

Ferguson had described this beforehand as “the toughest of all the quarter-finals”, illustrating a respect for Roma that has grown over the weeks since he expressed such surprise at their victory over Lyons, the French champions, in the previous round. All the scouting reports indicated that Roma exuded quality and would pose serious questions of United — not least in a tactical sense, given an unusual playing style that features Totti, a playmaker, as their farthest man forward. That is how it transpired, with the Italian team mustering 26 attempts on goal, scoring through Taddei, on the stroke of half-time, and Mirko Vucinic midway through the second half.

The great shame for United was that Scholes’s dismissal in the 34th minute left them a man short at a time when they seemed to have settled after a nervous start. Ferguson blamed Herbert Fandel, the referee, with whom he has a history, and Cristian Chivu, the Roma defender, but it is high time someone at Old Trafford had a serious word with Scholes.

For such a wonderful player, he is a liability to himself and his team when he throws himself into tackles, as he did from a very early stage last night. Viewed in isolation, the two fouls for which he was booked, on Christian Wilhelmsson and Totti, in the space of six minutes could indicate a slightly unfortunate sending-off, but as frustrating as the referee’s performance was at times, this was one of those evenings when a Scholes red card seemed inevitable.

Ferguson preferred to blame Fandel, who also sent off Roy Keane against José Mourinho’s FC Porto in 2004, and also Chivu, whose histrionics encouraged the referee to show a red card when it seemed that he might give Scholes the benefit of the doubt. Chivu scoffed at the suggestion. “It wasn’t my fault,” the Roma player said. “The referee got it right.”

The red card put United on the back foot again, having recovered their composure until that point. Michael Carrick had been a calming influence, but his team-mates looked uncomfortable in defence throughout and finally, a minute before half-time, their resistance was broken. They were caught napping by Mancini’s quickly taken corner, but it took a clever pass from Totti, inside John O’Shea, to find Mancini again in a crowded penalty area. The Brazilian winger beat Ole Gunnar Solskjaer and pulled the ball back to the penalty spot, where Taddei beat Edwin van der Sar with the aid of a sizeable deflection off Wes Brown.

It seemed that United’s principal objective might now be damage limitation, but that is not their style. They re-emerged after half-time with a new game plan, with Cristiano Ronaldo operating as a lone striker, supported from wide positions by Solskjaer and Rooney.

Ronaldo should have scored four minutes into the second half, after another incisive pass by Carrick, but in the 60th minute that much-needed away goal arrived as Rooney showed composure to chest down Solskjaer’s right-wing cross and beat Doni for his first goal in the Champions League proper in 17 appearances since his debut against Fenerbahçe in September 2004. Cometh the hour, cometh the man.

That away goal could prove priceless, but within six minutes, United were trailing again. A fierce shot by Mancini was too hot for Van der Sar to hold and, while the United defence stood still, Vucinic did not, sweeping home the rebound only four minutes after his introduction as a substitute.

A third Roma goal would have left United with a mountain to climb on Tuesday, but, despite Totti’s best efforts, it did not come, leaving Ferguson to wipe his brow with relief and start planning for what promises to be a dramatic evening at Old Trafford.

AS Roma (4-1-4-1): Doni — M Cassetti, P Mexãs, C Chivu, C Panucci — D De Rossi — C Wilhelmsson (sub: M Vucinic, 62min), S Perrotta, Taddei (sub: A Rosi, 82), Mancini — F Totti. Substitutes not used: M Ferrari, R Defendi, R Faty, S Okaka Chuka, G Curci. Booked: Perrotta.

Manchester United (4-4-2): E van der Sar — J O’Shea, R Ferdinand, W Brown, G Heinze — C Ronaldo, M Carrick, P Scholes, R Giggs (sub: L Saha, 77) — O G Solskjaer (sub: D Fletcher, 72), W Rooney. Substitutes not used: C Eagles, K Richardson, A Smith, Dong Fangzhuo, T Kuszczak. Booked: Scholes, Solskjaer, Heinze. Sent off: Scholes.

Referee: H Fandel (Germany).