Atletico Madrid have stumbled through the season so far, taking one step forward and then rapidly one step back.
Beating Manchester United would leave them dreaming of a first ever Champions League; defeat would reopen the debate as to whether Diego Simeone’s era is coming to an end.
The group stages were typical of the way the season has gone. They were on the canvas after losing twice to Liverpool and then at home to Milan. Then the away win at Porto that sent them through was hailed as one of their greatest European nights.