Many senior players were seen behind the dugout for their Carabao Cup win against Barrow in midweek.
"I said that I want all of them there," Maresca said on Friday. "The ones in the squad have to be there and the ones not in the squad have to be there too.
"You have to behave like a team and if there is a game, they have to be there.
"If there is a problem and some of them cannot come, then that is not a problem. I don’t know whether we say it is a rule but when there is a game, the players have to there.
"In terms of culture, I think it is quite normal that if my team-mate is playing a game, I am there before the game to support him and I am there after the game to support him in case he wins, loses, does well or does badly.
"It is normal for them to be there, whether it is the Premier League or Carabao Cup. If we want to create something then these small things are very important."