Mosimane is currently in Morocco doing his CAF Pro Licence, having been invited by Africa's governing body to do the highest qualification in coaching on the continent.
Mosimane was not on the bench as Sundowns took on AmaZulu in the Prince Mangosuthu Legacy Cup on Saturday, as assistant coach Manqoba Mngqithi took charge in the 2-1 victory.
The former Bafana Bafana coach, however, will be back when Downs take on Steve Komphela's Celtic side.
"He will be back on Thursday," Sundowns' spokesperson Thulani Thuswa tells KickOff.com.
"He was invited by CAF. It's only for a select few coaches who are invited for the course. Remember he was left with two modules to finish. He is busy with this one and then there will be one more after this. It takes a bit long," he adds.
Mosimane can certainly trust his technical team to prepare the team for the match against Phunya Sele Sele. Mngqithi and goalkeeper coach Wendell Robinson have tons of experience.
Sundowns, meanwhile, will be without Sibusiso Vilakazi, who has sustained a long-term injury.