The Portuguese tactician has stressed that the Spain international was not benched on Wednesday because he got in touch with Barcelona's Xavi and Carles Puyol
Casillas accused Cesc Fabregas of diving following his role in the brawl in the closing stages of the second leg of the Spanish Supercopa and the Madrid captain got in touch with his Barca colleagues afterward to explain himself.
Reports from Spain suggested that Mourinho had consequently decided to drop his captain from his starting XI for the match against Galatasaray as he deemed his actions to be a lack of support, but the tactician has explained that he just wanted to give back-up shot-stopper Antonio Adan some valuable playing time.
"Iker may call whoever he wants to. That's none of my business," Mourinho said to reporters, according to Marca.
"Adan needs to play. He is young and hadn't played a single minute with the first team before I arrived at Real Madrid. We believe he has the necessary quality to be a first team goalkeeper with Casillas.
"Adan played tonight [Wednesday] and did well. A goalkeeper's job is to make saves and allow the team to take points. His save in the final minutes allowed us to earn an important victory."
Madrid are unlikely to be in league action in Spain this weekend because of the ongoing strike that is affecting the fixture list.