Despite a relatively unsuccessful loan spell at Porto last season, Sarr has been given three starts by Blues head coach Thomas Tuchel, the latest coming on Tuesday night as the European champions edged past Southampton in the EFL Cup.
While Pastorello has hinted that the Frenchman could go out on loan in January, he believes that the 22-year-old has the potential to make a long-term impact at Stamford Bridge.
Speaking to Sky Sports News, Pastorello said: "I'm sure he will end up playing for this team because of his mentality, his professionalism, he's such a humble and lovely guy. He's very focused on reaching his target and his target is to be a Chelsea player.
"The winter market will arrive so we will decide with the club what is the best for him because he probably needs more experience before coming back but I'm 100% sure about him."
Sarr's solitary appearance in the Premier League came against Brentford earlier this month, the former Nice man impressing during a 1-0 victory over the club's city neighbours.