THERE is a staccato chant in football circles that runs thus: "Xavi-Inietsa-Pedro-Messi." The order of names can be altered but it almost inevitably ends up with Messi being pronounced in a higher note in anticipation of the demonstration of genius.

It is not unknown, though, for the Argentine's name to be followed by a sigh of unfulfilment.

This is the triumph and disaster of Barcelona. They play beautifully but they also play without what the cliché merchants call an end product.

They will play at Camp Nou for their very survival in the Champions League. Two goals by AC Milan from Kevin-Prince Boateng and Sulley Muntari ensure Lionel and his mates face a huge challenge in the return leg on March 12.

The surprise at last night's result is that any dedicated observer is surprised. This, after all, is a Champions League campaign that offers intrigue beyond the brilliance of Barca. It has been quietly assumed that the Catalan side is the dominant European power of the era. This does not survive cursory scrutiny. Barca can bedazzle but they can also be confounded. In the millennium years, Europe's premier trophy has been shared with a pleasing democracy, if that concept can be said to exist in a competition founded and sustained on the avarice of the big clubs.

Real Madrid, Bayern Munich, AC Milan, Porto, Liverpool, Manchester United, Inter and Chelsea have all won the trophy since 2000. Barca have won it three times since 2006, a praiseworthy achievement but they have not exerted the grip that Real Madrid did from 1956-60, Ajax (71-73), Bayern Munich (74-76), Liverpool in the late 70s or Milan (89 and 90).

Barca have never won the tournament in consecutive seasons so the idea of some Catalan dynasty is unproven when tested in the Champions League. They have been questioned in Europe already this season and failed to come up with an answer, only providing a late whisper in the deafening cauldron of Celtic Park and being beaten at the San Siro last night. They cling on, however, in a tournament that hums with interest and contains a pleasing variance of styles and possibilites.

Barca's major complaint last night was Craig Thomson's decision not to award a handball against Kevin Constant before Boateng thrashed in the first Milan goal. The official will argue that the ball hit Constant and was not intentional. Barca can argue all they want . . .

The second goal, however, was a simple example of how Barca can be exploited with a ball over the top and a thumping finish by Muntari. The Catalans ultimately limped from the field with fatigue matched by disappointment but there should be a collective realisation that Christian Abbiati was never forced to make an outstanding save.

The tiki taki, the mantra of Xavi-Iniesta-Messi invariably ended with a Milan boot making a decisive, blunt intervention, normally at the edge of the box.

The visiting players were incapable of firing the ball unsighted and unprompted into the area. AC Milan players did not fear the cross and they had no reason to rue their bravery. Massimiliano Allegri, the coach, did not have to exhaust his mental reserves to divine how Barca would play or how his time should negate them.

The answer lies in a collection of DVDs, most notably one marked Celtic-Barca November 2012. For example, last night Dani Alves found himself in space regularly on the right but always took a touch so he could ensure possession of the ball would subsequently be passed on to a colleague. One hesistates to lecture the aristocrats of the game on tactics but surely a speculative, flashing cross along the six-yard box with a forward being charged to attack the ball would bring occasional reward.

Instead, Barcelona played with a constancy that became wearily repetitive and were threatened when Milan broke. Stephan El Shaarawy could have made more of two first-half openings but Barcelona eventually succumbed to two strikes in the second period.

Barca only opted for desperation in the final moments when Gerard Pique was ordered forward without tangible result.

The result will quicken the pulse across Europe. Barca's dominance may be overrated by dint of being the side everyone wants to avoid. Their departure from the tournament would be welcomed by the other teams in a competition that offers an exciting diversity of styles.

Ther German challenge is strong: Bayern Munich are surely into the last eight, Schalke earned a valuable draw against Galatasaray and Borussia Dortmund are in an excellent postion after a scoring draw in Donetsk.

Real Madrid and Manchester United may not be of vintage stock but they will renew battle at Old Trafford with the added edge that Barcelona may not be in a later round to obstruct their progress.

There is also the fascinating factor of Juventus. If Bayern are characterised by a phyisical drive, Borussia by a pleasing fluency and United and Real by the contagious will and nous of their managers, the Old Lady of Turin has a marked pragmatic attitude. They believe there is no one way to play football but agree there is a solitary purpose: to win.

Barca, against all their principles, may have to swallow that truth whole and unadulterated.