Ramos was dropped to the bench for Real's victory over Athletic Bilbao just 24 hours after a disparaging interview he gave in the Madrid press.
AS says Schuster met with Ramos at the club's Valdebebas HQ for a no holds barred summit.
Ramos apologised to Schuster for the interview, while the coach told his defender that "my door is always open" and there is "no need to send messages through the press".
Schuster also explained to Ramos that he dropped him for the Bilbao game because "you said in the interview you were tired and were playing in pain, so I decided you needed a break".
He also said: "Do not stop believing in us, Sergio, because we believe in you. And you must realise you are a very important player in this team and you must produce the best Ramos because we need you."