McCarthy broke the news after Josephs asked to be excused from Bafana Bafana's upcoming Soccer World Cup 2014 qualifiers with Ethiopia and Botswana, as well as a friendly with Gabon next month.
According to McCarthy, Josephs is frustrated at playing second fiddle to Kaizer Chiefs' Itumeleng Khune.
McCarthy said in the Cape Times: "Moeneeb is a great professional, and if I was in his situation, I would have done the same thing.
"You do everything possible to fight for the number one spot, but you know yourself you are never going to be number one, because it's fairly clear it's Itumeleng Khune.
"He's (Khune) a great goalkeeper who's worked hard and put himself there... (but) in this country, there are a lot of great goalkeepers and you have to make it open for everyone to fight for the number one. It's clearly not like that, it's plain to see the manager (Pitso Mosimane) has his ideas of who is the number one, irrespective of other great goalkeepers around.
"So in an act of frustration it happens when you get to 30 and you feel you are not achieving your goals. It is better to continue to do what makes you happy, to play club football."
Bafana's record scorer added: "He is my roommate and he was asking for my input, and I said 'You are on your own. I don't want to advise you, make your decision, and whatever you decide, I am behind you'. When he explained his reasons, the man just broke down crying.
"I understand Moeneeb's issues and hopefully it will work out for the best and people's won't hate him," concluded McCarthy.
Josephs played 19 times for the national side.