Celtic will be without winger James Forrest for Wednesday's opening Champions League Group H match at AC Milan, the Scottish champions revealed on Tuesday.
Having missed Saturday's 3-1 Scottish Premiership win at Hearts with a sciatica problem, Forrest subsequently fell ill and was absent when the Celtic squad met up at Glasgow airport to fly to Italy on Tuesday morning.
However, midfielder Joe Ledley (groin) and his Welsh international colleague Adam Matthews (ankle) both travelled with the squad despite injury concerns.
"Unfortunately James is ill," said Celtic assistant manager Johan Mjallby.
"He has been feeling that sciatica problem lately but at the same time he is ill.
"It is brilliant that Joe is here. When I left the training ground he was struggling and we were pretty sure that he would not be able to make it, so that is great news.
"The scan has come back and obviously shown that he has a chance."