McTominay has taken his game to another level since leaving Manchester United for the Azzurri last summer.
"He feels more complete and knowledgeable and he's reaching a key stage in his career where he needs to decide his direction. He never had a primary role at Man United, while here we gave him one," Conte told reporters on Friday.
"He's worked hard and now he's a complete player. His improvement has been shared by the whole team. Otherwise, it would be hard to explain how we've earned 74 points."
"Napoli are back!"
Meanwhile, Conte has Napoli on track to stun Inter Milan and clinch the Scudetto this season.
He also said, "My message to everyone around the club is: stay united. Whatever happens tomorrow, there will still be three matches left, and we have a solid base - we'll be in the Champions League next season and that's important.
"Today we're fighting for the Scudetto and that should be a source of pride and joy. After just two years, Napoli are back competing for the top prize."
Napoli currently lead the table, three points ahead of Inter.