Calls for the Italian boss to name the 18-year-old in the starting lineup have grown louder, with fans chanting his name even though he was an unused substitute during Sunday's laboured 2-1 win at Cardiff City.
"He is ready to play, probably he will start tomorrow or in the next match," Sarri told reporters ahead of Brighton's visit on Wednesday. "In pre-season after four or five training sessions, I realised that Callum was a player with very great potential.
"In my opinion, in that moment he wasn't ready to play at this level, but during the season he has improved and he is ready.
"I want him to improve more because the potential is high. Callum is always in my mind... He is our future."
Chelsea have slipped down the table despite a strong start to the season, when they went unbeaten in 18 games, and fans have been typically vocal in their displeasure at Sarri and his methods.
"I don't know, probably we started very well and so our fans thought that everything was really very easy for us, but it isn't true," Sarri added.
Chelsea are currently sixth in the standings, a point behind fourth-placed Tottenham Hotspur and fifth-placed Manchester United in the battle for Champions League spots.
"We have to work to improve, I think that if you take a coach with my characteristics, you have to work.
"I'm not happy, of course... I can understand well the frustration of our fans."
(Reporting by Rohith Nair in Bengaluru; Editing by Hugh Lawson)
