It was the final kick of the match when Blaise Matuidi gave Paris Saint-Germain the encouragement to believe this tie may not be over. His shot took a slight yet decisive deflection off the nearest defender and Victor Valdés in Barcelona's goal could not improvise quickly enough to stop it squirming over the line. The drama had been unremitting in the final stages and the last act came so late there was not even time for the match to kick off again.

For Barcelona it meant a night of conflicting emotions bearing in mind how close they had been to going into the second leg in a position of even greater strength. They should still be regarded as the favourites but any sense of satisfaction has to be tempered by the knowledge that Xavi Hernández's penalty to make it 2-1 had come in the 89th minute of normal time. From that position a side of this refinement will consider it wasteful not to have finished the job.

They will also have to consider the possibility that Lionel Messi will not take any part at Camp Nou on Wednesday week because of the hamstring problem that cut his night short. Javier Mascherano will definitely be missing after one booking too many, though damaged knee ligaments would have ruled him out anyway.

Messi, even on a night when he lasted only the first half, still made a significant contribution, scoring the opening goal after a sublime pass from Dani Alves, the game's outstanding performer.

Zlatan Ibrahimovic equalised in the 79th minute, albeit from an offside position, but Carlo Ancelotti's side almost contrived to throw it away when their goalkeeper, Salvatore Sirigu, brought down Alexis Sánchez to give Xavi the chance to restore the lead from the penalty spot.

It was a breathless finish and PSG deserve acclaim for their perseverance even if Matuidi's goal did carry a considerable slice of good fortune. The French league leaders had played with great verve and never seemed to lose belief even in those passages when the game appeared to be heading away from them.

Ibrahimovic played the last half an hour as though he would be personally affronted not to make a lasting contribution against his old team. Lucas's ability to run with the ball made him a formidable opponent and David Beckham gave everything until the speed of the game became too much for a player his age. Beckham had just been booked and was conspicuously starting to fade before his 70th-minute substitution, just as the game had picked up pace again.

He had worked diligently, from the base of midfield, and can probably be excused if his ability to shape matches is not what it used to be. At 37, there were some distinguished touches but it was always going to be difficult against a midfield of such expertise.

Barcelona have the knowhow of a side who have reached the semi-finals in each of the last five seasons. PSG, in contrast, are sightseers at this level. This was also Barcelona's first match with Tito Vilanova back in the dug-out after two months of cancer treatment in New York. "With Tito, we are much stronger" was how the front-page headline of Diario Sport put it. The players had promised they would mark it with a classic Barcelona performance and, by half-time, everything had been going to plan.

Messi was at the hub of it. It is easy sometimes to get lost in the blizzard of statistics surrounding the Argentinian but he has now scored Champions League goals in 20 different cities. In total that is 258 goals in his past 251 matches for the club or, this season alone, 57 in 45.

The latest was classy in its creation, clinical in its execution. As soon as the chance arrived, it felt almost inevitable that he would bury it.

Alves had spent most of the first half playing as a right-winger rather than the full-back. The pass he delivered with the outside of his right boot was sumptuous, weighted to perfection with just the right amount of curl applied. A ball that distinguished was always going to be too inviting for Messi to pass up, especially on his left foot.

For long spells the players in luminous orange and yellow – a team of Barcelona's prestige should never wear such a ghastly combo – pinned back their opponents. Yet PSG could reflect on an impressive opening half an hour. They had broken forward with pace and purpose. A post had spared Sergio Busquets an early own-goal and there were other times when the home side's counterattacking style stretched the opposition defence.

They also had the fortune that is sometimes needed against Barcelona. Even ignoring the deflection for the final goal, Ibrahimovic's follow-up effort after Thiago Silva's header had come back off the post should not have been allowed.

Matuidi's luck did not extend throughout the whole game, however. A booking means he will be suspended from the Camp Nou return.