Speaking today, manager Derek McInnes said: "Funso will be out for the best part of three months and Craig Bryson will miss around four weeks.
"We had 13 players at training today so it’s a challenge. Jon Gallagher is fine though, and is available for Saturday."
The Belgian midfielder, who joined from Scunthorpe after an intense transfer battle involving Hibs, has played ten times for the Dons this term, while former Scotland and Kilmarnock midfielder Bryson arrived from Derby County and has featured five times in all competitions.
Ojo and Bryson join Scott McKenna, Ash Taylor and Scott Wright, who have all suffered injuries in the early part of the season.
Wright is expected to miss the rest of the season while McKenna is due back later this month and Taylor has been pencilled in for a return to action at the start of October.
The Dons boss also discussed a possible return for Tommie Hoban. The Irish defender spent time on loan at Pittodrie last season but suffered an injury that limited his chances.
Released by Watford over the summer, he has been linked with a return to Aberdeen as he looks to complete his rehabilitation.
McInnes added: "We’ve offered Tommie the chance to come up and train and he’s said he’ll take up the offer at some point."