Manna was speaking before Friday night's win against Cagliari brought them within touching distance of Serie A leaders Inter Milan.
Before kickoff, Manna offered his picture of the situation in Napoli.
On Kevin De Bruyne's return after long-term injury, Manna told DAZN: "He is in good physical shape and has trained hard. At the same time, it is difficult to say that he is better than when he arrived, because he has not played for four months.
"He is a high class player and very intelligent. I am convinced that he can contribute to the team in these matches."
During the winter window, Napoli signed Alisson Santos.
Manna also said, "Alisson is a humble player who has worked hard to reach this level. He has the qualities we sought to strengthen the team."
He also commented on coach Antonio Conte and his situation.
"Considering how we have worked during the year and the challenges we have had, I can say that the coach's contribution has been decisive.
"He has one year left on his contract and there are no problems. We are very pleased with what has been achieved in the last two years."
In conclusion, the sports director spoke about Scott McTominay's future.
"Scott has two years left on his contract and we have a very good dialogue with him and his representatives," said Manna.
"He wants to stay in Napoli. We are having a dialogue, but there is no rush. This is not something we need to inflate right now. He is very important to us and we value him highly."