Gallagher is set to sign with Atletico Madrid later on Tuesday.
Maresca was asked about the England midfielder ahead of facing Real Madrid and said: "Nobody is going to be a regular starter because if I say someone is going to be a regular starter, I think it is a lack of respect. For them, they need to work day by day very hard and show me and convince me they are to play but nobody knows.
"In this moment, there is something between the club and the player; an agreement to stay or to leave. These kinds of things happen in every club, every summer and in the end the final decision will be good for everyone. Hopefully the final decision will be good for Conor and the club."
On talk of Chelsea selling off their academy graduates, Maresca added: "But this is not Chelsea's problem, these are the rules. All the clubs at this moment are compelled to sell players from the academy because of the rules. It's all of the Premier League clubs' problems."