When the away goals rule was first introduced in 1965 it was because, to score one, travelling teams often had to overcome the fright of bumpy flights, bumpier pitches, cacophonous home crowds and, just occasionally given the climate of the time, the shadowy presence of totalitarian secret police.

None of those stopped Manchester United scoring at the San Siro on Tuesday. Just Julio Cesar, poor finishing from Ryan Giggs and Alex Ferguson's reluctance to really exploit the rule and attack in the last 20 minutes. The perfect plan but with no pay-off. And now the apparition of an away goal unnecessarily haunts Old Trafford like so many ruined return legs in the past. Only a fully-focused performance will exorcise it. But it needn't have been so.

It might have been like at the Bernabeu. There, Rafa Benitez's battleplan killed the game as a spectacle before Yossi Benayoun's header all but killed the tie as a contest. Hard to criticise though. Benitez merely achieved what Ferguson attempted – if in, admittedly, a contrastingly colourless fashion – and again proved that for all his faults he is, as the Spanish media put it, the Garry Kasparov of European ties. If Real Madrid fail to score at Anfield it won't be because of the aura of playing away.

The rule also hangs over the other two ties involving English clubs, but for a different reason. Arsenal and Chelsea completed their objectives expertly at home and if either score first in Italy next week, such will be the gap, any excitement from Juventus or Roma will be extinguished. Exactly what Michel Platini's plan for European football is trying to prevent.

As such, it's worth re-assessing one of Uefa's most archaic rules. When the concept was created it was to make competition run smoother as, previously, deadlocked ties went to a play-off. The Cup Winners Cup was the first to see it applied, Budapest Honved defeating Dukla Prague in the 1965-66 second round. That success saw it implemented in the Fairs Cup the following season and then for the European Cup in 1967-68. Curiously, the first Champions Cup tie it decided – along with Valur's victory over Juenesse Esch – was Benfica's visit to Glentoran. The side that featured Eusebio, and that came within a late Alec Stepney save of denying Manchester United Matt Busby's dream in the final, first needed a technicality to knock out Northern Irish part-timers.

The rationale behind the rule however was to reward rousing football. Now that air travel is so routine Ryanair actually try to stop you bringing luggage onto planes and charge you for doing so, it's difficult to contemplate how unaccustomed even footballers were to the novelty – and nerves – of flying. Not just that, but how unintentionally ignorant they were of foreign opposition. Even 13 years after the away goal was introduced, in his exceptional memoir of 20 years covering Brian Clough – Provided You Don't Kiss Me – Nottingham journalist Duncan Hamilton describes the difficulty of negotiating international operators to determine any sort of information about the likes of Romania's Arges Pitesti.

Imagine the mid-60s then. In such unknown surroundings, the default setting was defence. First legs would often be the first opportunity to properly assess opposition so best to play it safe and let them set the attacking agenda. The away goals rule, at first, teased sides out. Now, of course, footballers are so used to flying that in six-day periods when they don't have a game they will just as easy jet out to Dubai for an exhibition game, as Manchester United did last season. Not just that, but the regular coverage and competitors of the Champions League mean they're by now over-familiar with opponents.

The value applied to an away goal on account of its assumed rarity value then is highly debatable. Indeed, the evidence denies it. Taking the five years of European Cup competition after the rule was introduced and the five years up to the end of last season for comparison, away wins are now much more likely. Between 1967 and 1972, 16 per cent of ties ended with the travelling side victorious. Today it's 21 per cent, and that's discounting the group stages where the difference is much more pronounced. Similarly, in the domestic game, the likes of Liverpool and Chelsea have better away records than home.

The question then is why away goals should be so costly when they've become so commonplace. Especially since, far from merely deciding ties, they have psychologically dominated them. To the extent a 2-1 defeat away is, absurdly, often considered favourable to a 0-0. With Alex Ferguson predictably downplaying the matter, it was left to Jamie Carragher to emphasise their effect.

"Away goals are massive in Europe and that means Real Madrid have got to get one now in the second leg. Hopefully if they come at us it'll give us more space and make it easier. That's just what we came for."

While away goals admittedly add an intriguing tactical variable that managers have to think around, too often their solution is a negative one. Like many such incentives – such as three points for a win – they breed protection and paranoia rather proactively trying to get one.

In this round the rule can now only benefit Arsenal after their unravelling of Roma but it was a subject a purist like Arsene Wenger was vocal on at the start of the season.

"The rule was created when teams went away, with no television, played 10 defenders and kicked every ball into the stand. Now I believe the tactical weight of the away goal has become too important.

"Teams get a 0-0 draw at home and they're happy. Instead of having a positive effect it has been pushed too far tactically in the modern game. It has the opposite effect than it was supposed to have at the start. It favours defending well when you play at home.

"We proposed to Uefa at some stage that the away goal should only kick in like it does in the Carling Cup, in extra-time. It would still favour the team who plays at home because they play 30 minutes more there. At the moment when you get 0-0 at home, and then go away, the team who plays against you absolutely has to score. They have to come at you."

"We" being a biennial conference of Uefa coaches – including Alex Ferguson – where a warm reception to the idea was reported.

The curiosity then is if Ferguson listened so attentively to Wenger at that conference, why he didn't to those quotes in September – leaving himself open to the exact scenario the Arsenal coach outlined. Why – the first half an hour at the San Siro notwithstanding – did Ferguson go against Wenger's rationale and play it so conservatively when the cost of conceding was minimal, only to leave his team the onus of opening up at home when it is at its most expensive? Why not put on Wayne Rooney earlier as Inter tired?

Granted, Ferguson can point to last season's beating of Barcelona but the responses are Rotor Volgograd, Monaco and Real Madrid. His side now leave themselves open to the stunned silence that descends when a visitor thumps in an away goal. Likewise Roma and Juventus against Arsenal and Chelsea. Liverpool at least have the cushion their own. It was a fear, however, that Inter's Javier Zanetti has already played on.

"They will not be very relaxed. They are aware that things can get really dangerous if we grab a goal."

And the most frustrating aspect would be that, on the evidence of last week's games, this is an underwhelming Champions League season. By rights, it should be there for Manchester United or Barcelona, two teams whose quality is in sharp contrast to the competition. By recent record however, that's not how the Champions League works. United's superiority over Inter on Tuesday ran parallel to their domestic dominance. The worry is they have yet to make it count and that in Europe Benitez – and possibly now Guus Hiddink – have proved adept at denying home form to manipulate the nuances of knock-out football. Ferguson could yet be undone by one of its most archaic.

mdelaney@tribune.ie