The striker has arrived from Barcelona and featured in today's hammering by Celtic in the US.
Asked about his plans for the 18 year-old, Maresca said: "The idea with Marc, with all the young players, is to have a look now during the pre-season and then to make a decision altogether.
"I think Marc is doing well and he's one of the guys in this moment is going to stay with us and not going to go somewhere."
On holding back Raheem Sterling today, the manager insisted: "Raheem is working well since day one. We are just trying something different. The other day with (Tyrique) George and today with Misha (Mudryk). It's just to see things. It's not any reason why Raheem isn't starting, it's just to see things.
"Carney (Chukwuemeka), for instance, started the other day and started today. Lesley (Ugochukwu) was inside, Angelo was inside; just to see all of them. Just for that."