Ahead of Euro 2012, rumours had been rife over strained relationships in the Spain camp due to the rivalry between Real Madrid and Barcelona, and at one stage Vicente del Bosque openly acknowledged that there were issues between Gerard Pique and Sergio Ramos.
Xavi's father has now revealed that the problems in the national camp were serious, and that Spain were able to successfully defend their European Championship crown was down to the diplomatic efforts of Casillas and Xavi.
Mourinho had said in March that he had "no problems" with Casillas as speculation of a fall-out raged, but Joaquin Hernandez told COM Radio: "Iker had many problems with Mourinho because Xavi and Iker didn't want to end their friendship. The problems came to light and everyone knows about it.
"Had it not been for Iker Casillas, Xavi and Del Bosque, the national team would never have achieved what they have. It has been very complicated at times because of the Clasicos.
"Friendships between players were about to end. There were rows. There were issues with Arbeloa, Xabi Alonso and Sergio Ramos and how they behaved towards their team-mates. The behaviour of some players was inappropriate. Luckily, Iker and Xavi intervened."
Hernandez also responded to the suggestions his son had looked tired during Euro 2012.
"Xavi has played 81 games this season," he said. "It's a brutal schedule, and involves travelling all around the world, but he was fine. It's said that he wasn't in a good state physically, but that's not true."
