Sarri suggested Callum Hudson-Odoi could be involved against PAOK but insisted the 18-year-old needs to show improvement in his defending if he is to earn a regular place in the side.
"He has to improve, I think he has to improve a lot," Sarri added. "First of all, the defensive phase. He has to work, he is very good in the one against one, but he has to learn to move without the ball.
"He's a very, very good player, and now he has to study, to improve, to work. But I think this is normal because he is 18. I want to find space for him but it's not easy, because we have 28 players. It's not easy to put him in the starting 11.
"It's very difficult, but I'll try to find the space for him. He is in the 18 players for the match; I don't know if he will start."