Osimhen was omitted as Napoli suffered a 3-0 defeat to Verona, fueling speculation about his potential departure from the team.
Conte was asked about the striker's absence and replied: "This is a question you have to ask the club and not me. I see that Osimhen has been training separately since his return.
"You have to ask the club, absolutely not to me. I said it straight away, I put myself as a spectator on this story.
"But beyond a single player you certainly need to have a different attitude, with more personality, more desire. I've found some kids who struggle in the difficulty and this is a serious thing because you don't train them in a very short time, you have to have time and patience. You have to try to make them grow in terms of mentality."