Celtic had captain Scott Brown sent off as Barcelona avenged last season’s defeat in Glasgow with a narrow win.
Cesc Fabregas was the match-winner, heading an Alexis Sanchez cross past Fraser Forster with 15 minutes left.
The breakthrough for the Catalans only arrived after Brown had been shown a straight red card for kicking out at Barcelona forward Neymar.
Brown flailed a foot that caught the Brazilian on the arm and, despite Celtic protestations, he was dismissed.
Barca’s victory may well have come regardless of Brown’s dismissal, with the Spanish champions enjoying 82 per cent possession, and the hosts being forced to survive a sustained period of pressure.
It was only Celtic’s second ever home defeat in the group stage of the Champions League, the first also having come at the hands of Barcelona in 2004.
Celtic’s sense of injustice over the red card would scarcely have been diminished by Neymar’s part in the winning goal.
He picked the ball up in space, deep in home territory, spun and fed Alexis, whose perfect cross was headed back across Forster by Fabregas and into the net.
Few inside Celtic Park would have begrudged the visitors that lead had it come before the game took that ugly turn, but as it was, it was greeted with rancour.
What was all the more galling for the home fans was that it came just minutes after they had seen Victor Valdes pull off the save of the match to keep out a blistering effort from substitute James Forrest, with Charlie Mulgrew heading narrowly wide from the resultant corner.
There was some solace for the home support as Forster brilliantly denied Neymar a goal on two occasions in the closing minutes.
Remarkably, it had taken until the stroke of half-time for Barcelona – missing the talismanic Lionel Messi – to force a save from Forster.
The goalkeeper on that occasion pushed a Xavi free kick away for a corner, but until then the protection offered to him by his team-mates had been absolute.
In the face of relentless Barca probing, the back four and the four in front of them stood firm as the visitors passed their way to the edge of the Celtic penalty area only to find it largely impenetrable.
That led them to try their luck from further out, but first Neymar dragged a shot wide after dancing his way in from the left wing and then the magical Andres Iniesta sold Mulgrew an outrageous dummy but blasted off-target.
Forster would have struggled to reach Neymar’s deft re-directing of a Dani Alves cross, but happily for the keeper it spun outside the post as he sprawled to his left.
Unlike last year’s astounding 2-1 home win, however, there was to be no fairytale ending for Celtic, as gallantly as they fought.
