Krasic was dropped from the starting line-up against Genoa, while Chiellini struggled to impress.
"Krasic is improving, he's been great over the past few years and has special qualities," Marotta said.
"His performances so far this year, however, are not level with his ability. We need to get him back to his best.
"Boss Antonio Conte's good at making the most out of his resources and will find the right way to bring him back.
"Chiellini is an international player, he's often carried Juventus in games. He might have had difficulty in certain cases, but he's not on trial.