"I find it very strange and amazing that Orlando Pirates could know what was in our [registration] book. How did they know to go straight for Schut's card?" he asked
"The game was loaded against us, we wouldn't have won it anyway," he told reporters after the defeat for the Absa Premiership champions.
Pirates protested that an outdated card had been presented for Schut, leaving Sundowns now to answer possible charges.
Each season, every player registered with the Premier Soccer League is given a card that must be presented for inspection before the match.
The league also supplies teams with a neat hard-cover folder with plastic sleeves for the cards so that they are easily transported and displayed in what is usually just a formality before matches.
Cards must be taken to the games and the opposing team has an opportunity to inspect them before the match.
Some clubs check them more thoroughly than others even though identity fraud in the top flight of the South African game was left behind in a bygone era.
The question of why Sundowns, who have a bevy of officials around the team, had an outdated card for the Dutch defender in their folder was not answered and is as intriguing as the coach's conspiracy theory.
Although when one reporter put forward the suggestion he was offering up a conspiracy theory, Mosimane retorted: "I did not say that."
Pirates, who must pay R10000 to lodge their protest, might decide it is pointless to proceed after they won the game, and with a 3-0 scoreline.
But the PSL could pursue charges because the rules state "it will be misconduct for a club to field a player without a valid ID card or alternatively fail to make such ID cards available for inspection prior to the match".