By FOX Sports Staff
Kovacic, 18, was signed from Dinamo Zagreb for a fee of around €13 million just before the closure of the transfer window.
The youngster primarily plays as an attacking midfielder and his ability has been lauded by a number of figures, including the likes of Zvonimir Boban, Milan Rapaic and club president Massimo Moratti.
Cassano added to the chorus and gave a glowing review of the midfielder's performance during training. The teenager played in Inter's 3-1 defeat to Siena over the weekend but demonstrated a remarkably good technique for a player of his age.
"I saw him in the first training session, and you can tell he's got great ability," Cassano told the club's official website.
"Inter have spent big and spent well on him - he's going to be here for the next 10 years.
"He'll become a great player, I'm 100 per cent sure of that."
Cassano has also paid attention to the transfer activities of city rivals AC Milan, who signed controversial striker Mario Balotelli. The Italy international does not have the best of opinions towards his compatriot but does not wish to speak ill of the 22-year-old's decision to return to the Serie A.
"There's one difference between Mario and I - he probably likes being in the paper, whereas I don't.
"But I've done worse things in my life. I left training, I drove my car onto the pitch - you name it, I did it.
"He's a good lad though."
Cassano and Kovacic could next feature for the Nerazzurri against Chievo on Sunday.