The Uruguayan winger came on as a 72nd minute replacement for Sibusiso Vilakazi in a 3-0 league win over Dikwena at Loftus Versfeld on Saturday.
Mosimane reckons Sirino has a first touch on par with Sundowns attacker Khama Billiat.
"I know what he is capable of and that's why we brought him here," said Mosimane, who recruited the 26-year-old from Bolivian side Club Bolivar.
"He has got that first touch that Khama has. You saw the pass he made to Percy [Tau]. He is quality."
'Jingles' was also encouraged to see the link-up play between Aubrey Ngoma and fellow new signing Jeremy Brockie against Stars.
"I was happy with the delivery from Aubrey against Platinum Stars to find Jeremy Brockie. That's quality. That's exactly what we really need for the Champions League."
Mosimane's men next visit Premiership title rivals Kaizer Chiefs at FNB Stadium on Saturday night looking to extend their four-point lead at the summit.