Sirino was magical in the 2-1 win over AS Togo-Port in the Caf Champions League at Lucas Moripe Stadium on Friday night.
The 27-year-old inspired Sundowns to their first win in the group stage of the Champions League by scoring one goal and assisting the other.
“I have been waiting for this performance,” Mosimane said.
“It was his kind of a game. He came out of his shell in this match. He turned it on from the first minute. He is getting more confident and has adjusted to the way we play. He carried the team.
“He did that probably because the other two guys (Khama Billiat and Percy Tau), who normally carry the team, weren’t around. We have been waiting for somebody to carry the team when Percy and Khama aren’t around. Normally it’s Percy who turns the volume up a lot.
“What I am happy about is the goal he scored. He is starting to score and at times he passes too much when he can score
“He must carry the team now. It’s his chance. That’s why we brought him here. This is the performance I went to see in Bolivia.
"He is capable of this and more. It’s good for him to give us confidence and hope.”
This victory now puts Sundowns on five points to make up for their slow start that had seen them collect a paltry two points from their first three matches.
Mosimane joked with the AS Togo-Port coach that can he please do him a favour by beating Horoya on August 17.
“The Brazilians” will take on reigning African champions Wydad Casablanca in Morocco on the same day and then end the group stage against Horoya in Atteridgeville.
Mosimane views the Guinea side as their biggest threat in the fight to reach the quarter-finals as he has conceded that Wydad will likely top Group C.
But he has to improve his side’s defence if they are to make the knockout stage.
“What I am not happy about is the goal we conceded in the last minute (against AS Togo-Port),” Mosimane said.
“It looks like it’s becoming a trend. In Horoya we were winning 2-1 and they scored with six minutes remaining. Against Chiefs they scored with a minute left.
“It shows that we lose concentration at critical times. I have to work on that. It’s mental sometimes.”
Sundowns will start their Premiership title defence on Saturday at Loftus Versfeld in Pretoria with a titanic tussle against Chiefs.
This will be a tricky season for Sundowns as they not only have to balance their domestic ambitions with this Champions League campaign but they will also return to continental football later this year in a congested calendar which will see the continent’s premier club competition run for six months next season.
“We are not ready, let’s be honest,” Mosimane said.
“We are only on week four of our programme. We take time. If you win on week four, it’s much better and it shows you’re on the right path. We’ll get better with time.
“We are preparing for the marathon. You can’t just prepare a team and then it’s ready now and when the Champions League starts in December you’re tired. We are building momentum.”