Marmoush strengthened his case for greater involvement by scoring twice in City's 3-1 pre-season victory over Atletico Madrid in Seoul on Sunday.
However, despite his impressive performance, the 27-year-old faces another battle for a starting place once the competitive season begins, with Erling Haaland expected to remain the club's first-choice striker.
Marmoush has started just 22 Premier League matches since arriving from Eintracht Frankfurt in January 2025, while making another 15 appearances from the bench. He has scored 10 league goals during that time but has struggled to establish himself as a consistent starter.
Maresca, who recently took over from Pep Guardiola, compared Marmoush's situation with that of goalkeeper James Trafford, who left City for Leeds last week after finding regular first-team opportunities difficult to come by.
"Players work every day, they want to play so when they don't play they are not happy," Maresca said.
"Omar did not play a lot last year so his desire is probably to play more minutes.
"It doesn't mean that he isn't going to play more minutes here but it's also his decision, and he needs to decide."
Marmoush's two-goal display against Atletico will have given Maresca another reminder of the attacking options available to him as he prepares to begin his first competitive campaign in charge.
City's preparations have been complicated by the absence of several important players. Haaland, Rodri and Rayan Cherki were among those missing from the club's Asian tour, while England internationals Elliot Anderson, Marc Guehi and Nico O'Reilly have also been unavailable following their involvement at the World Cup.
Despite those absences, Maresca believes his squad is responding positively to his methods and that progress is being made ahead of the new campaign.
"I'm very happy. Especially because the players since we started have been open-minded," he said.
"They want to understand and want to learn why we do things.
"I know that when you join a new club you try to install new patterns or different ideas. The most important thing is we are getting better.
"The path is a huge path to improve things. But I can see we are trying what we do in training, and we are getting better at that."
City will face Arsenal in the Community Shield on August 16 before opening their Premier League campaign away to Bournemouth on August 23.
