The England left-back has been linked with Manchester United in recent days.
Maresca said ahead of Sunday's season kickoff against Manchester City: "Chilly is with us but he has not been training for the last few days because he has been ill. With Chilly it is quite clear, even though I love the way he is, the problem is that he is struggling to find the right position with us.
"This is the reason why he did not play against Inter last week.
"'This morning we had 22 players training and if you ask all of them they want to play against City on Sunday but that is impossible. When you train every day and not get any minutes it is not good for them or for me and I need to make a decision. Probably it is better to leave and go and get minutes.The transfer window is open so we will see what will happen."