The Tunisian mentor returned to management after a short spell away from the game by joining the Moroccan Botola Pro League side ahead of their new season.
In his most recent post, Nabi led Amkhosi to the Nedbank Cup title - for their first trophy in ten years.
But he leaves Raja after just five games, that includes two wins, two draws and a defeat.
Posting online, the head coach explained that he was compelled to part ways with the club after their "visions regarding how to build the future eventually diverged".
"As-Salamu Alaikum, following the end of my collaboration with Raja Casablanca club, I wanted to speak out in order to close the subject and avoid unnecessary controversy," he posted.
"The club's identity, its history, its demands, and its playing DNA deeply matched my football philosophy. It was this alignment that convinced me to join this great club.
"I took over the team in a particularly complex and difficult context, but thanks to Allah, the work of the players, the staff, and all parts of the club, we managed to save our season by achieving the goal of qualifying for the CAF.
"I approached the new season with a clear vision, a lot of ambition, and a desire to build a project worthy of what Raja represents. This vision was initially shared by the management and the different parts of the club, and it was on this basis that I accepted the project.
"However, with the evolution of the project and sporting choices, some directions changed, and our visions regarding how to build the future eventually diverged.
"I fully respect this decision, and I do not want to turn a difference in sporting vision into a controversy. Raja is above all of us. When I arrived, I said that a team is never built on a single individual. I still believe that. Neither the coach, nor the player, nor anyone else is or will be above the institution.
"I thank my players for the respect they showed me and their willingness to have a great season, my staff, and everyone I worked with during this time.
"My thanks go to the loyal Raja supporters and the Ultra Eagles and Green Boys groups for the warm welcome, respect, and support I received.
"I wish the club, its players, its management, and my colleague who will take over all the best for the upcoming season. I sincerely mean that.
"I leave Raja Casablanca with respect and now look toward the future. Thank you."
