We know one thing for certain: Porto are really going to have to go for it.
With a two-goal deficit to make up against Chelsea in Tuesday night's second leg, the Portuguese champions have little to lose from all-out attack with a Champions League semi-final place at stake.
Luckily for them, their two leading goalscorers, Mehdi Taremi and Sergio Oliveira, are set to return to their team having missed last week's 2-0 loss through suspension.
The return of a duo who have scored 35 goals between them this season and set up a further 20 could well prove the basis for an astonishing turnaround.