Benfica's midfield schemer Rui Costa has been ruled out of action for a month due to a thigh problem, meaning he could miss both UEFA Champions League games against Celtic.
The 34-year-old, who rejoined the Lisbon side after a 12 year exile in Italy over the summer, has aggravated a thigh problem and is now set for a spell on the sidelines.
The former Fiorentina and Milan star first suffered the problem in a league game against Boavista three weeks ago, and exacerbated the injury in Benfica's 4-1 win over CD Das Aves on Monday.
Rui Costa will definitely miss the trip to Glasgow to face Gordon Strachan's Bhoys on October 17, and is also likely to be absent when the Scots make the return trip to Portugal on November 1.
The thigh rupture sustained by the midfield star has sparked controversy in his home country with some reports attributing the secondary injury to mistreatment of the player after the initial problem.
Rui Costa's absence could be keenly felt by Benfica after they only managed to earn one point in their opening two European games against FC Copenhagen and Manchester United.