Having been beaten to a through pass for away striker Marc McNulty, Jullien redeemed for his error by racing beyond keeper Vasilis Barkas and clearing the shot before it crossed the line.
However, as he slid to clear the ball his trailing left-knee collided full on with the base of the post, making an alarming thwack in the process.
The 27-year-old was moved to the side of the field while he was attended to by the club’s physios before leaving on a stretcher.
It certainly puts his participation in Saturday’s Old Firm encounter at Ibrox in severe doubt as Celtic wait to see if there is any potential long-term damage.
Jullien has already been absent for three months this season due to a back injury.