Pioli is in his second spell in charge of Fiorentina after leaving Al Nassr over the summer.
He said this morning in his media preview: "I'm thrilled to be back playing in Florence. Antonio (Conte, Napoli coach) is among the best in the world for the identity he brings to his teams and the titles he's won. We've prepared a lot of strategies, but ultimately it'll be the players who make the difference.
"They've (Napoli) won two Scudetti in three years and have strengthened tremendously. They're the favourite again this year and can compete in the Champions League as well. Tomorrow, the pitch will tell how big the gap is.
"We're a good team, and so far, our level is similar: we've had two weeks to prepare and some absences. I'm very confident, even though we know how strong our opponents are.
"They've had excellent coaches and many great players. They've always had great players, with great height and jumpers. They're a complete team today, but I'm still convinced we can compete, playing our game and giving it our all."
Asked if he feels privileged working with Moise Kean, Pioli added: "Very much. He's very strong and I think he still has a lot of room for improvement off the ball."