The heartache came late, but then Celtic's Champions League run this season has flashed through the emotional spectrum at such breakneck speed that there should have been no surprise.
A result that betters Benfica's at Barcelona in their final Group G encounter with Spartak Moscow at Celtic Park next month will take them into the last 16, a position they would have willingly accepted before a ball was kicked in the competition, but last night it was almost so much more.
With 20 minutes remaining, they were through. Georgios Samaras had scored in the 32nd minute to cancel out Ola John's early opener. They weathered storms from the skies and storms from their opposition, but then, with the game in the 71st minute, Ezequiel Garay smashed a volley into Fraser Forster's goal and ensured the nerves will fray until the final ball of the group is kicked. With five minutes to go, their talismanic figure Victor Wanyama was booked for a foul that will rule him out of their final game with Spartak.
Indefatigability. It will come to be the defining quality to describe the Celtic collective. No matter what happens from here, manager Neil Lennon has drawn everything from his players. In the pouring rain, they ran and slid and blocked and fought. This was a more ferocious kind of fight than the 180 minutes of heartache and heroics against Barcelona. It was more basic, and it was from a growing sense of belief that similarly characterises this campaign that they fight their way back into this game.
It had not started well.
By the seventh minute Celtic, rocked back on their heels, were behind. Benfica bore the drive of a team who had to win, at home, where their own record is very good. Only two minutes had passed when a mistake by Samaras allowed Oscar Cardoza to run and try his luck from 25 yards. It went over, but it was a warning.
It was also symptomatic of sloppiness in the opening stages. Adam Matthews erred on the left in the seventh minute and from there, in the blink of an eye, Celtic were behind. Eduardo Salvio seized possession, crossed into the middle and with Scott Brown unable to clear, John shot so quickly that there was barely time for Forster to register as the shot flew past his right hand side.
It was a lead that should have been doubled on the half-hour mark. Salvio was again the creator, slipping a fine pass behind a leaden-footed Celtic back line that saw Efe Ambrose out of position. Cardoza had only Forster to beat but dragged his shot wide of the near post. It was massive miss. Within two minutes Celtic had drawn level.
Three times they had scored with headed goals before their trip to Portugal, records matched by only Manchester United and Ajax in this year's competition. Number four came in the 32nd minute. Charlie Mulgrew fired over his right wing corner and with Gary Hooper holding his position next to Artur, Samaras was allowed to head into an empty goal from two feet out. Celtic had their foothold and they held it firm as they positioned themselves on the back foot.
Enzo Perez shot wide from distance, Salvio crashed an effort over the crossbar after good work by Jon and Andre Almeida cut in and shot over. Forster stood up well to John to deny the Benfica star with his left foot and the impressive Nemanja Matic volleyed over the visitors' crossbar.
Benfica had given warning after the interval of what was to come. Lima produced a superb run down the Celtic right, cutting inside and then shooting past Forster, only to be denied on the line by Matthews. It was Benfica's 18th attempt on goal, to Celtic's two. Luisano shot over the bar from close range. Forster did well to deny the ever-dangerous Lima and in the 70th minute, an excellent cross from the same player flashed across the Celtic six yard area with Salvio somehow failing to get a touch.
A minute later came Benfica's second goal, and their two central defenders were creator and scorer. The initial header came from Luisano, and it was perfectly placed for Garay who crashed his powerful volley past Forster.
Wayama was denied by Artur in the home goal in the 74th minute and from the rebound substitute Kris Commons was denied. Salvio shot narrowly over Forster's crossbar and moments later Cardoza's free-kick was tipped over by the former Newcastle goalkeeper.
Man of the match Salvio.
Match rating 6/10.
Referee V Kassai (Hun).