Spalletti's future is in doubt over tension with Napoli president Aurelio de Laurentiis.
Marotta told Radio RAI: "I'm lucky enough to know both quite well.
"I hope for the good of football that they can continue to work together are two added values of our football. The fact that they separate makes me a little bitter.
:"They have done a huge undertaking, the result of great competence and professionalism."