The Nerazzurri triumphed at the San Siro thanks to a brace from Rodrigo Palacio, and are now in control of their Europa League last-32 tie ahead of next week's return leg in Romania.
The Croatian was making his first start since joining the club from Dinamo Zagreb during the January transfer window.
"Kovacic is clearly a player with great quality and everyone can see why we invested in him," Football Italia quotes the 37-year-old as saying.
"He immediately realised what I wanted from him, to be a deep-lying playmaker. He is a humble lad and it's up to me to help him settle."
Kovacic cost Inter £12.9m.