Giorgos Giakoumakis could be out of action until the end of the year.
The striker was bought from VVV Venlo to provide cover and competition to Kyogo Furuhashi but has so far only started two matches.
Giakoumakis appears to have suffered a knee injury during his substitute appearance away to Dundee on November 7 and has since undergone surgery.
Kyogo has barely had any break since the J-League started in February but it looks like Ange Postecoglou will be short on alternatives during the hectic December fixture card.
Discussing Giakoumakis, The Sun reports the Celtic boss saying:
He had to have a clean out of his knee. So he’ll be about two, three weeks.
At the moment Albian Ajeti is the only alternative striker option available to Postecoglou.
Mikey Johnston and James Forrest have been used in emergency circumstances in the past but are both more effective on the wing.
Owen Moffat has made the bench once this season in the SPFL with the only other options being the totally untested Joey Dawson and Adam Brooks.