Playing at this level of the Champions League is like signing an important contract – it’s all about the small print.

Read the big phrases, get excited by the special-offer clauses, but miss the detail and you’ll be turned over.

You’ll get a rusty Ford Cortina and an loan-shark APR instead of a Range Rover and easy, stable repayments.

Small print, detail, is at the heart of whether Manchester City can eliminate Barcelona this season – as opposed to the series of crucial, naive errors which left them defeated home and away against a far less impressive Barça last term.

Go back to the first leg last February.

Manuel Pellegrini now admits that he was more fixated on not conceding an away goal than he was by prioritising playing on the front foot, putting Tata Martino’s side under pressure – turning it into a rousing, racy English version of a big European night.

“Last season we wanted to put the brakes on Barcelona in the first leg because the value of the away goal is almost always determining in the Champions League” Pellegrini revealed at the weekend.

“This time we’ll go for the match from the very outset – albeit with consideration for the fact that we’re playing a dangerous opponent”

That tactic was the first mistake. City surrendered the initiative. Martin Demichelis was given a man-marking job on Leo Messi. Largely he did it well until the 53 minute.

There followed a series of errors from City which turned the entire tie.

Jesus Navas thought he’d been fouled. So did his team mates. City ‘stopped’.

Not stock-still but they relaxed, they expected the whistle. There was a drop in concentration and intensity. Barcelona whisked the ball upfield.

City’s first mistake – assuming that the whistle would go. Not playing flat-out until it did.

The next belonged to Vincent Kompany. Before Navas lost the ball Messi had looked lazy and self-indulgent.

He was isolated upfield, significantly offside. Barely trotting back.

Meanwhile Iniesta was racing out of his own half with the ball at his feet.

Passing immediately to Messi wasn’t an option.

But Kompany wasn’t aware of where the Argentinian striker was. He’d ‘lost’ him, mentally.

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So with Iniesta running towards him Kompany did the ‘natural’ thing of jogging backwards to try and get in line with Demichelis in the hope that City’s midfield would intervente make the first attempt to close Iniesta down.

As Kompany urgently jogged backwards, Messi had begun sprinting to try and get onside.

The combined effect, the defender going backwards, Messi running towards him, cut the time needed to get the striker onside.

Iniesta noticed, waited, slid the perfect pass into the striker and suddenly City were sunk.

Demichelis tried to compensate, made the ‘last-man’ tackle and though he was unfortunate that the referee called it a penalty, rather than a free kick, it was suddenly 10-man City v Barcelona with a spot kick.

Details. Small details. Already turning the tie.

Another such was the Neymar substitution. All season he’d played on the left. This time Martino brought him on down the right. In the 16 minutes he was on the pitch he regularly combined with Dani Alves, already playing like a winger, to overwhelm Gael Clichy. Alves nearly scored.

Neither Pellegrini nor City, albeit with ten men, knew how to react. Nothing was done, Neymar and Alves combined again in the match’s last minute and suddenly the single away goal was two. Total disaster, but foreseeable and preventable.

The second leg was much, much more competitive. City played with a great deal more poise, intelligence and conviction.

Until the key moment.

Cesc Fabregas’ through-ball to his long term ‘partner-in-crime’, Messi, for whom he’d been creating goals since they were 14, should have been intercepted and recycled forward by Joleon Lescott. To do so was simplicity itself.
But somehow he ends up deflecting the pass straight into the path of Messi who scores. 3-0 and goodnight Vienna.

There’s a haunting image of Pellegrini, in the Camp Nou stands because of his red card in the first leg, head in hands. Frustrated, desolate. Disbelieving.

There are individual elements which, objectively, push forward the likelihood of City performing much more dangerously this season.

Kun Agüero had zero impact a year ago – now he’s fit and in lovely form.

City intermittently posed a real goal threat in both of the ties last season, Edin Dzeko in particular pulling a brilliant save from Victor Valdés – already a three time Champions League winner. At that stage teh Catalan already had 104 outings in the competition under his belt.

Tonight, Ter Stegen, 22, [six Champions League matches] will keep goal for Barcelona. Patently a very good young keeper, superb with his feet, Manuel Pellegrini’s scouts will have noticed him flapping at corners and cross balls this season – noticeably in conceding the second goal in a 3-2 defeat at PSG in the group.

No Touré tonight – but unquestionably the possibility of Kompany, Fernandinho, Dzeko, Bony or Lampard adding a headed goal at some stage in the two ties. Stegen faces a test of fire.

What about a health-check for those who don’t see Barça regularly?

Neymar’s form this season has been sublime – as has his partnership with Messi. “We look for each other with the ball, all the time” Messi told me about the intuitive link-play which was such a part in the 42 goals scored in the eleven straight wins between defeat to David Moyes Real Sociedad and the appalling performance in losing 0-1 at home to Málaga on Saturday.

BUT, for the last three or four performances the Brazilian’s accuracy, ruthlessness in front of goal and consistency have dipped – noticeably. Bad timing.

Suárez has been playing with wonderful cleverness and selflessness – a modern Henrik Larsson. The only thing missing, now, is a clinical finish. Will it come now?

Rakitic has been the element to make everything tick. “Barcelona are less elaborate now than they were at the peak of Xavi, Iniesta, Busquets” Pellegrini says. “More direct .. but still as dangerous because of the quality of their players”

Rakitic is one of those footballers who seems to be everywhere, can tackle. pass, play divine wall-passes, has a goal in him and won’t be shy of the power of English football.

His form is a central building block for Barcelona. If he’s dynamic they press and win the ball and use it much more dangerously.

I suspect it’s worth thinking about both teams to score, possibly twice each, worth thinking about Kun and Messi to exchange ‘anything you can do I can do better’ goal-moments.

If City make similar errors, if they haven’t learned, matured – they’ll be beaten twice.

If Barcelona play anything like they did against Málaga they’ll really suffer at the Etihad. In fact, in that case, they’ll be beaten.

But when that ‘Champions-hymn’ shimmers out, it’s Pavlovian for Barça. They’ll be up for it and we’ll have fun watching this tie. Better balanced than last season, more goals, but everything still revolving on details. Tiny details.

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