Celtic midfielder Beram Kayal has been ruled out for the remainder of the season following ankle surgery.
The Israel international was stretchered off in the closing stages of the 1-0 victory over Rangers last month after being hurt in a challenge from Lee McCulloch.
Kayal was initially expected to be sidelined for a month, but further scans revealed serious damage that required surgery and he is now facing at least four months out.
A statement on Celtic's official website read: "Beram Kayal underwent surgery last night on his injured ankle and the club can confirm that, unfortunately, our worst fears have been realised and Beram will be out of action for at least four months."
Celtic boss Neil Lennon admitted it was a major blow to lose the key midfielder.
"This is very sad news for Beram," said Lennon. "He has been brilliant for us and instrumental in our performances during the season.
"He will definitely be a big loss for us, but more importantly we are disappointed for him to be missing such a large part of the season at a time when he was playing so well.
"Clearly his health and fitness is now our priority and we will be making sure he gets our total support during the coming period."