"He still has not made a mistake," the Austrian told the APA news agency.
"He is a new star. If he has a car that is right, he can be world champion."
Ricciardo won his first grand prix in Canada last weekend, two places ahead of his high-profile teammate Sebastian Vettel.
Berger knows Vettel well, having given the German his first seat in formula one in 2007 when he co-owned the Toro Rosso team.
"We know how good and fast Vettel is, a four-time world champion. But at the moment, Ricciardo is the measure of things for the team," he said.
"If Ricciardo had not had the penalties at the beginning of the season, he would be just behind Lewis Hamilton in the world championship," added Berger.