The 21-year-old, who arrived from Dinamo Zagreb in the summer, last featured in the 3-1 victory over St Johnstone on 23 January.
Simunovic, who missed Sunday's League Cup semi-final defeat by Ross County, also had a spell on the sidelines in the first half of the season.
Kris Commons is close to a return from a muscle injury.
The midfield playmaker, 32, has missed the last three matches and manger Ronny Deila said Wednesday's visit to Aberdeen "would probably be too soon" for a return.
Celtic captain Scott Brown made his first appearance in two months as a late substitute at the weekend.

The observatory claims radio interference from household appliances would pose "a significant risk" to the Lovell Telescope's operation.
Developers deny their plans would cause an "unacceptable impairment" to the observatory, described by Cheshire East Council as "internationally important".
A government inspector will now hold a series of hearings into the proposals.
Cheshire East councillors rejected the plans for 119 homes in Goostrey last year, concluding the proposals would "result in impairment to the efficiency of the Jodrell Bank Radio Telescope".
In representations to the council, Simon Garrington from Jodrell Bank said: "Radio interference has an impact on almost all the observations which are carried out.
"Interference is correlated with human activity, whether due to intentional transmissions or unintentional leakage from a wide range of electrical and electronic devices.
"The proposed development itself is likely to generate interference which exceeds the internationally agreed threshold for what constitutes 'detrimental interference' to radio astronomy observations."
The proposed development site, off Main Road in Goostrey, is 1.95 miles (3.14km) from the observatory.
Representing Cheshire East Council, Christopher Katkowski told the inquiry that the protection of Jodrell Bank was "a matter of global significance", because the Lovell Telescope's work is "internationally important".
The inspector, Gareth Jones, admitted that he was "no expert" in radio astronomy, but he may be making a visit to the observatory to understand its work as part of the process.
Gladman Developments launched an appeal after the council refused its application, claiming there was "no evidence" their plans would cause a significant increase in radio interference.
The firm argues that the village of Goostrey already produces radio interference, so 119 extra homes would not make an unacceptable difference.
Richard Kimblin QC added that the situation may have "some apparent complexities" but insisted the developer's case was quite simple: not enough homes are being built in the east of Cheshire.
In a statement to Cheshire East Council, the company said it was "prepared to work with (Jodrell Bank) and consider any reasonable mitigation measures that they might suggest to alleviate their concerns."
The government planning inspector will make recommendations to Communities Secretary Greg Clark, who will make a final adjudication.

He'll be blasting off in December and will spend six months on-board the International Space Station (ISS).
So, we thought now would be a good time to tell you our top astronaut facts...
Celtic's Croatian defender Jozo Simunovic will be absent for four to six weeks with knee ligament damage.
[NEXT_CONCEPT]
A public inquiry into whether a planned new housing development would "impair" Jodrell Bank's telescope has begun.
[NEXT_CONCEPT]
The European Space Agency's first British astronaut, Tim Peake, is completing the final preparations before his mission to space.