Ange Postecoglou hit out at referee Don Robertson for failing to deal with a "terrible" tackle on Yosuke Ideguchi at Alloa.
The Celtic midfielder is set for a spell on the sidelines as his manager suggested the injury - sustained following a challenge from Mouhamed Niang - is worse than he first thought.
Ideguchi was forced off following the incident and Niang was shown a yellow card during Celtic's Scottish Cup fourth round victory at the Indodrill Stadium on Saturday night.
