Chiefs are sitting on top of the log with 45 points in 20 matches, while Pirates are in third place with 39 points in 21 matches.
Sundowns are in second place with 41 points in 20 matches, four points adrift of Chiefs.
Chiefs have the title in their hands going into the business end of the season.
Mosimane is appealing to Sundowns fans to rally behind the Buccaneers on Saturday.
Mosimane reacted from Egypt where his team is preparing for the CAF Champions League quarterfinal first leg match against Al Ahly on Saturday. He says the Highlands match will be physically demanding.
– Report by Vincent Sitsula