Celtic left-back Emilio Izaguirre suffered a broken leg during the club's Clydesdale Bank Premier League victory at Aberdeen.
The Honduran left-back was carried off on a stretcher after going down in agony following a sliding challenge from Peter Pawlett.
Manager Neil Lennon revealed tests had shown up a fracture with the club soon confirming Izaguirre had broken his fibula.
Further tests will reveal whether Izaguirre requires surgery on his right leg.
The injury happened when the 25-year-old fell awkwardly following the challenge early in the game, which Celtic won 1-0 courtesy of a 74th-minute goal from Anthony Stokes.
Lennon said: "It's a huge blow for us to lose him and we don't know how long he is going to be out for.
"He is being assessed at the minute and we'll know whether he requires surgery and, if he does, he will be out for three months anyway."
Lennon held his head in his hands when he was told the initial diagnosis that Izaguirre had suffered a suspected fracture.
"You can always tell by a player's reaction and Emilio is not a player to feign injury," Lennon said.
"So the concern was immediate and he was taken into the dressing room and looked at and the word came out it was a fracture."
Source: PA
