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.
Footage showed the 22-year-old following through after winning the ball initially and coming down hard on the Parkhead star's ankle.
Postecoglou revealed his January signing is still feeling the effects of the challenge and the manager feels referee Robertson should have "addressed it on the day".
He told Celtic TV : "He’s not great. I said after the game it wasn’t too serious but to be fair I didn’t really get a good look at him.
"It was a terrible tackle and one which should have been addressed by the referee on the day.
"He hasn’t come out of it too well and will be missing for a little bit as well. He’s still pretty painful now.
"The kind of character he is, for him to stay down and come off I knew it was significant.
"I was optimistic it wasn’t too bad but as everyone can see from the footage it was a tackle that shouldn’t have happened and should have been addressed by the referee on the day.”
