Napoli coach Maurizio Sarri was delighted with their 4-2 win over AC Milan.
Arek Milik struck twice for the Azzurri.
Sarri said: “Milik really impressed me, as a lad and as a player. He's still settling in and trying to learn the language, but he's a sharp guy who picks things up quickly anyway.
“Is he the new Gonzalo Higuain? No, it would be unfair to compare a world class striker to a 22-year-old who is just starting his journey. I am sure he'll have a great career.
“As for Mertens, right now he's in great shape and so I preferred to start with him, but there's no specific hierarchy. He deserved to play tonight, we await Lorenzo Insigne to push his way back into the line-up."