Sarri is returning to Lazio for the new season after replacing Marco Baroni.
At a coaching summit today, Sarri spoke with local reporters ahead of his presentation - which is likely this coming week.
He said, "Nuno Tavares is the only unknown in the defense that I will find, he is strong but anarchic, if we manage to frame him he will become very strong.
"(Nicolo) Rovella? I had said that after 50 games as a low point, he would become a top. He lacks a bit of dribbling but he is very strong. (Mateo) Guendouzi is a contagious animal for those who play next to him, he needs the leash because he can't stop at 100%, he has to go further."
Sarri also commented on European champions PSG, stating: "PSG taught the world a lesson, they sent away top players, they lowered the wage bill by buying very young players with whom they had courage and won where (Lionel) Messi and Neymar had not won."