Sterling joined City earlier this month for an initial £44million, with the deal rising to a potential £49million based on add-ons.
The England international faced intense criticism before and after the completion of his move, with many believing the 20-year-old will struggle to match the aforementioned valuation – one which makes him the 12th most expensive footballer in history.
Speaking after Sterling scored his second and third goals in two pre-season friendlies, manager Pellegrini insisted he was in no doubt the forward would justify his hefty price.
“He is a very good player; that’s why we brought him to our team,” the City boss told reporters.
“He has a lot of things we didn’t have in our squad. If you watch the way he played [in the 8-1 win against Vietnam], he has a lot of pace and I am sure in the future he will demonstrate why we paid so much money for him.”
On the heavy victory over Vietnam, the Chilean added: “I was very surprised because it is not easy to score eight goals but Vietnam is a team that must prepare for qualification for the next World Cup and they have time.
“They start playing in September or October so have to work hard but they have very good players.”