“Surprise came in and all we needed was for him to score that goal,” Mosimane said after the game at Loftus Versfeld in Pretoria.
“I could have put him in earlier but I kept him (on the bench).
“He came on and showed his experience, and that’s what we needed.”
Moriri, who replaced Hlompho Kekana in the 83rd minute, scored three minutes later, after Stars had drawn level shortly after half-time.
Cuthbert Malajila opened the scoring 27 minutes into the clash, before Camaldine Abraw cancelled the advantage.
Moriri secured the victory which lifted Sundowns two points clear at the summit of the league standings.
“Football is amazing. Sometimes we get it all wrong but tonight, the substitutions were unbelievable,” Mosimane said of his decision to go for the victory.
“At one point I said, ‘I can stay on top of the log with a point’.
“But it’s not in my nature, I threw in all the strikers. Sometimes it works, other times it backfires.”
Mosimane admitted he was wary of Stars before the kick-off and would have settled for a draw, but added he was delighted to have grinded out three valuable points.
“Let’s be honest. In the second half I think Stars could have taken it. Let’s give them credit and be fair.
“I was thinking of a draw and told myself I could take a draw and still be on top of the log, but we got the points when it mattered most.”
The Brazilians headed into the game on the back of a shock defeat at the hands of league new-comers Polokwane City last weekend, and Mosimane reserved special praise for the club’s resilient supporters.
“I’m happy. What I’ve seen and what has changed, is the people behind us.
“They never give up. When it was tough they kept singing and they kept us in the game. Last week against Polokwane City they never left, they kept singing.
“The supporters are helping us. It’s a different culture, unlike those ones who shout ‘substitute, substitute’.”
Bafana Ba Style look comfortable at the top of the Premiership table, two points ahead of a chasing pack of three — Wits, Moroka Swallows and SuperSport United.
What pleased Mosimane most, however, was the way in which his team came back from their defeat to City and produced the kind of display which wins titles.
“Sundowns never used to come back in games like this… they would give up and we would lose,” Mosimane said.
“We were disappointed from that game against Polokwane City, where five players never played well. Tonight was another story. The substitutions were good. That’s championship mentality.”