Chilwell's contract runs until 2027. The England international has made 106 appearances for Chelsea since joining from Leicester City in 2020 and helped the west London side win the Champions League in the following year.
The 27-year-old, who usually plays as a left-back for Chelsea, fell down the pecking order after Spaniard Marc Cucurella arrived in 2022. Chilwell was sidelined by injury last season, making 21 appearances across all competitions.
"Chilly (Chilwell) has not been training for the last few days because he has been ill," Maresca told reporters.
"It's quite clear, I love the way he is but the problem is that he struggles with us a little bit to find his best position."
“This morning we had 22 players training, and if you ask all of them they will say they want to play against City on Sunday but that is impossible.
"When they train every day and do not get any minutes, it is not good for them or for me, (as) I need to make a decision. It is probably better to leave and get minutes (elsewhere). The transfer window is open so we’ll see what happens."
