Away goals could prove decisive in the return legs of both Liverpool-FCB and Lyon-Barca but will both away teams on Tuesday regret not attacking more?
The spectre of the away goal haunts every Champions League knockout tie.
Even when an away goal is not in play, the very thought of it pervades matches; coaches on either side too aware of its significance.
The onus on the home team is not to concede one, as we saw on Tuesday night when Lyon and Liverpool held Barcelona and Bayern Munich scoreless.