The Croatian youngster arrived at the San Siro as an attacking midfielder in January, but impressed in a deep-lying role.
He will now be moved further up the pitch again, with Mazzarri predicting that that will be his best position.
"I think he [Kovacic] can really make a difference in the final third," Mazzarri told reporters.
"I'm trying to give him some advice; he's young and needs time to develop. I think he's the sort of player I'd like to see operating a bit further up the field.
"He's a versatile player who can play in three positions. In the future I think he could play his best football in the hole, or out wide in a front three."
Inter take on Catania later today.