Liverpool have been rocked by injuries to key players Xabi Alonso and Dan Agger.
Alonso has struggled with the problem for several weeks and, although he left Portugal with his left foot in a brace, at first Liverpool's medical staff believed his condition was not be serious.
Agger's place was taken by Sami Hyypia, whose lack of pace was exposed by Porto for their opening goal.
Alonso and Agger were both taken to a Merseyside hospital after the team returned yesterday and last night Rafa Benitez's worst fears were confirmed.