The 23-year-old central defender, who sat out final weekend’s Premiership draw in opposition to Hibs at Parkhead, has torn his hamstring.
The injury caused Simunovic to drag out of Bosnia and Herzegovina’s World Cup qualification double-header with Belgium and Estonia.
Bosnian group physician Reuf Karabeg showed the analysis.
He mentioned: “Head trainer Mehmed Bazdarevic and I talked to Jozo’s physician and from him we were given get entry to to the entire documentation at the injury’s situation.
“The findings of the X-ray display a rupture and he has a hematoma which is 4 centimetres lengthy.”
It is a big setback for Simunovic, who were determined to get his Bosnian world occupation up and operating after controversially switching his allegiance from Croatia previous this yr.
The defender has already ignored a number of fixtures this season because of injury and Celtic supervisor Brendan Rodgers will likely be keen to determine a restoration timescale ahead of some large video games.
Celtic’s first fit after the world spoil is in opposition to Dundee at Parkhead on October 14.
They then talk over with Bayern Munich on Champions League responsibility earlier than taking over Hibs within the Betfred Cup semi-final.