Emanuel Pogatetz's season is over after is was revealed the Middlesbrough defender needs surgery to repair a facial fracture.
The 23-year-old Austrian international was stretchered from the pitch in Basle last night with a suspected skull fracture, and although that proved not to be the case, his injuries will require an operation next week.
'Emanuel suffered a badly broken nose and a fracture to the maxilla, a bone at the side of his left cheek,' a club spokesman confirmed.
'He will have an operation some time next week and will miss the rest of the season.'
The injury is a significant blow to the former Bayer Leverkusen player, who joined Boro in an £1.8million move last summer.
Pogatetz, who had five stitches put into a facial wound after a clash with Bolton's Kevin Davies on Sunday, was hurt as he challenged for a high ball with Basle midfielder Mladen Petric during his side's 2-0 UEFA Cup quarter-final defeat.
He collapsed in agony and after lengthy treatment on the pitch, was carried off on a stretcher and taken straight to hospital.
Initial fears that he had fractured his skull were dispelled in Switzerland and he was allowed to fly home with the rest of his team-mates early this morning.
Pogatetz was taken straight to Middlesbrough's James Cook Hospital on his return, and surgery was recommended.
He was at the club's training headquarters this morning sporting a badly bruised cheek, and faces a lengthy recovery period.
Physio Grant Downie was quick to praise all those involved in the player's treatment both in Switzerland and back on Teesside.
'The medical back-up at the ground was good, the Swiss authorities were very helpful and the team at the local hospital were very good,' he said.
'Boro's medical team were, as usual, efficient, making sure he received the appropriate treatment as soon as possible.
'It's appropriate we should thank all concerned for the way this injury has been dealt with.'
Pogatetz has become a key figure in the Boro squad, having played on the left of both the defence and the midfield, as well as a central defender, where he lined up last night.
Boro's defeat at St Jakob Park left them with a tough task on their hands to reach the semi-finals with the second leg to come at the Riverside Stadium on Thursday, although the Austrian, nicknamed 'Mad Dog' by his team-mates, will be reduced to the role of spectator.