Celtic manager Martin O’Neill will decide later today whether striker Chris Sutton can fly to Portugal tomorrow with the rest of the first-team squad.
The England man was forced to miss Saturday’s 2-1 win at Motherwell after contracting a virus which has also affected his family.
Sutton is anxiously awaiting the results of blood tests which will dictate whether he can travel or not for the vital Champions League Group E clash.
O’Neill will be desperate for the frontman to play after his inspirational form this season alongside Henrik Larsson has catapulted him to the brink of an England recall.
But if Sutton fails to recover John Hartson is line to make his Champions League debut against Porto.
The Welshman has still to get off the mark since in four first-team starts since his £6m move from Coventry City.
But Hartson impressed at Fir Park at the weekend and the Celtic boss believes he, Steve Guppy and Momo Sylla are getting closer to peak fitness.
O’Neill said: "For them to get another 90 minutes under their belts was absolutely satisfying, no doubt about it."
The Northern Irishman will bring back skipper Paul Lambert, flying winger Didier Agathe and in-form midfielder Alan Thompson after resting them on Saturday.
But Dutch winger Bobby Petta looks certain to miss out after recently suffering a recurrence of his hamstring injury.