Anthony Stokes will miss tomorrow night's Europa League clash with Atletico Madrid due to a thigh strain.
The Celtic striker picked up the knock in training yesterday and is already a major doubt for Sunday's Old Firm clash with Rangers at Ibrox.
Whether Stokes would have started in the Spanish capital is another matter but, with the 23-year-old missing, Neil Lennon's attacking options are reduced to choosing between Gary Hooper, Georgios Samaras and new Bhoy Mohamed Bangura.
Celtic were finally given the green light to go ahead with the match yesterday when UEFA threw out Sion's appeal to be reinstated.
The Swiss side fielded five players in the two matches against Celtic who were signed during the summer despite the club being subjected to a transfer ban from FIFA.
Sion are likely to take their dispute back to the Court of Arbitration for Sport but were given little encouragement from Michel Platini, who Sion have prepared a criminal complaint against over their exclusion.
The UEFA president said: "This is against all rules of sporting fairness. This is ultimately about protecting clubs, the players and football itself. We have clear rules and regulations that all clubs know before they enter our competitions."
The Sion appeal has deflected attention away from Celtic's visit to Madrid and a rematch with the club they faced in the semi-final of the 1974 European Cup.
Ex-Celtic skipper Billy McNeill called that Atletico side scum but Hoops CEO Peter Lawwell is keen to play down the events of 37 years ago.
He said: "Regardless of what has happened historically, we have a responsibility to ensure Thursday evening is a celebration of football."