Given Benfica had scored two away goals in Athens - courtesy of Diogo Goncalves’s stunning free-kick and Rafa Silva latching onto Dani Ceballos’ poor defensive header - Arsenal needed to strike twice or face elimination.
The odds looked stacked against Mikel Arteta’s side, but Tierney lashed home in the 67th minute before Pierre-Emerick Aubameyang got his second of the night three minutes from full-time by heading home Bukayo Saka’s cross.
“We all make mistakes all the time – sometimes they get punished and sometimes they don’t, but in European competition they are going to [get punished] and they did,” said Tierney.
“We bounced back the best way we possibly could and I think it is a good step for us to show we can face adversity, come back and go through.
“We never seem to do it the easy way. But credit to the boys we had some tough moments out there and some setbacks but to bounce back, score and go through to the next round, is all that matters.
“We are taking it game by game. We are not looking too far ahead, we have a big game on Sunday [against Leicester] as well. The games are coming fast right now so we can only look at one game at at time.”
Arsenal were the better side for both of their two legs against Benfica and, when Aubameyang opened the scoring last night after 21 minutes, it looked like they could cruise to victory.
Arteta’s side however, just as they did last week in Rome, made life difficult for themselves and left it late to go through to the last-16.
The result is a huge one for Arsenal - who sit 11th in the Premier League and are already out of both the Carabao Cup and FA Cup - as it keeps their season alive.
And Aubameyang also believes the manner of their win in Athens could help the Gunners as they try to salvage a difficult campaign.
“When you concede a second one, you know that you have to score two goals again, so it’s really hard, but as I said, we showed character and we kept calm during the whole match,” he said.
“It could be very good [for the rest of the campaign]. I think in this difficult season, hopefully this will give us some hope, but also some confidence for the future that we can do comebacks like this.”