Barcelona pulled off a stunning comeback at Estádio da Luz on a night of UCL that saw the Catalan giants come back from 4-2 down to win 5-4.A Benfica fighting for their lives after a single win in their last seven UCL matches at this venue gave a lesson in finishing to the visitors just two minutes into proceedings as a long diagonal ball fell to Fredrik Aursnes on the edge of the box.
He cut in for Vangelis Pavlidis to shoot in his second UCL goal of the season from close range, but Barcelona earned a penalty within minutes of that setback as Tomás Araújo' clipped Alejandro Balde's heel in the box.
Cool as ever, Robert Lewandowski deceived Anatoliy Trubin with a hop before striking into the bottom-right corner for his 86th career penalty conversion from a possible 96.
A couple of minutes later, Gavi was played through on goal by a deflection and forced a reflex save from Trubin. Barcelona might have pressed on from there, but their comedy of errors soon resumed, with a Benfica ball over the top seeing Wojciech Szczęsny brainlessly charge out of his box and collide with Balde.
That left the way open for Pavlidis to run the ball into an open net, and it would go from bad to worse for Szczęsny when he floored Kerem Aktürkoğlu after the young Turk broke through the lines. Pavlidis stepped up to complete his hat-trick with a calm conversion down the middle.
Barcelona survived the rest of the half, except when Raphinha had a clear view to shoot wide having rounded a Benfica mistake, and then came out at the break with both intent and energy.
Jules Koundé was played in on the left by a ball over the top but skied an instinctive effort that would have reduced the gap to one goal.
A bit more composure, and Lamine Yamal might have scored where the Frenchman failed, but he could only fire over drastically when he picked up a lofted pass on the edge of the Benfica box.
At the hour mark, Barca boss Hansi Flick made a double change to try and salvage some pride from a dark night in Lisbon.
And the fightback was firmly on almost immediately, with yet another surreal addition to the scoresheet, as Trubin's routine kick downfield flew straight onto the head of Raphinha and straight into the net, giving Barcelona newfound belief.
That was immediately dispelled, however, as Benfica scored a fourth, Tomás Araújo's cross coming into the box and finding Andreas Schjelderup, whose attempted square was deflected into the net via Ronald Araújo.
Barcelona simply would not lie down and die, and they were awarded their second penalty of the night, as Nicolás Otamendi felled Yamal in the area.
He placed the ball in the same position to present the finish for a nervous Benfica. Then it was a step too far for the Lisbon side: Pedri produced a cross out wide to the back post with his free-kick delivery and Eric Garcia headed in right beneath him.
But more drama was yet to come in deep injury time when Benfica had a penalty appeal turned down, and Raphinha broke Benfica's hearts as he put their chances of direct qualification for the Round of 16 into real jeopardy, all but sealing Barcelona's own prospects of doing so.