Sundowns will visit Makhulong Stadium for a crunch fixture against Highlands, which will be their third match in just seven days after earlier facing Al Ahly and Stellenbosch FC.
Mosimane raised fears about the sort of battle his side has on their hands, while also confirming a number of injury doubts to key players.
"You need energy at Makhulong, of which we don't have. You need player mobility, which is what we are really struggling with," said Mosimane.
"You also need mental strength to face a tough Highlands – you know they don't pull out of tackles; you know the story, they are strong, and they mark man-to-man, they go with you wherever you go.
"So, you need that. But we have the mental strength, I think you saw [against Stellenbosch], but we don't have the energy or the legs. We don't have player availability.
"Mkhulise played 15 minutes [on Wednesday] and ended up being carried out on a stretcher; Langerman has a bone bruise, so let's see how he responds.
"Themba Zwane has a hamstring and a shoulder, you could see he couldn't even celebrate after the match, while Sirino has a hamstring – I don't think those two will be available.
"If they are on the edge between making it and not, I would not take the risk to play them because we have another game on Tuesday. So, we'll see how we deal with the injuries and obviously on Saturday we'll do late fitness tests in the morning."