Not since Willie Young scored Arsenal's winner against Hajduk Split at Highbury to win a UEFA Cup second-round tie on away goals more than 30 years ago have they overturned a first-leg deficit in Europe.
They have never done it in the Champions League, but must start now if they are to progress to the last eight.
"To score away from home is still a massive advantage in the UEFA rules and that is why we are confident. To lose 1-0 away is a terrible result because you know, if you concede one, it's nearly over.
"We have scored and that to me is a massive difference. This time, if you score one, you are through if you don't concede. It is a tricky game but we know we can score goals. We want a better defensive performance."