The defender is again being linked with a move away this summer, with Italian champions Napoli keen.
Ahead of yesterday's Club World Cup round of 16 win against Benfica, Maresca said: "All the players who are here with us, I would not want to lose them.
"But, as we have said several times, when the market is open, unfortunately anything can happen. You can buy a player or sell him. Trevoh returned to us in January, if we earned a place in the Champions League among the top four, it is also thanks to him. He helped us a lot."
On Chalobah's future, Maresca added, "He's also played a few games here at the moment. He's with us, we're happy with him. Then, as I said, unfortunately, when the market is open, anything can happen, but not just for Trevoh but for all 25 players in the squad."
Lakeimouz
18
Head coach please we need Trevoh Chalobah You can't be doing that bullshit experiment on the field