Brazilian defender Nascimento slotted the 25th-minute spotkick against Arrows in a 1-0 win for the Absa Premiership leaders at Loftus Versfeld Stadium.
Tau would have likely relished the chance to bolster his tally from the spot, as he is tied with Polokwane City striker Rodney Ramagalela on 11 goals at the top of the PSL scoring charts.
Mosimane, however, is not about to change things around in the home stretch of the title race for the sake of an individual.
He said: "It's not about Percy. The guy [Nascimento] hasn't missed. Why change him?
"The guy has never missed. You can see he takes it the Brazilian way. He is smart. He has got a way of taking it. It's not about blasting. He has never blasted. He is smart, he has the technique.
"Percy understands. Maybe when we wrap the league he might have it."
Sundowns' victory over Abafana Bes'thende pushed the Tshwane giants six points clear of Orlando Pirates at the summit with three league games remaining.
The CAF Champions League participants will next battle Maritzburg United at Harry Gwala Stadium on Sunday for a spot in the Nedbank Cup final.