The manager of the Boys in Green, Giovanni Trapattoni, did not name Ward in his 23-man squad for the game against Brazil next Tuesday, despite the 24-year-old being the only left-back to play regularly in the top-flight.
"Trapattoni picks the squad," McCarthy said, according to The Express & Star.
"If Stephen Ward is playing well for me in the Premier League – which he is – then it’s up to the manager of the national team to decide to pick him, not me.
"All Wardy can do is what he’s doing for me. I don’t say anything because if anyone says anything to me about my squad, I tell them to ‘Foxtrot Oscar.’
"No one else picks my team and I have no intention of trying to pick anyone else’s."
He added: "Kevin Foley was Player of the Year for us last season and kept being picked in squads without playing, so Wardy just has to keep playing in the Premier League.
"He has to stay in the first team, because if he doesn’t, he has no chance of being picked. I have empathy for the managers, because it’s always the players not in the squad who make the controversial story.
"It’s like that here – Sylvan Ebanks-Blake was in the team for 16 games and the first time he’s not, I get asked about it.
"It also becomes a controversial story when former Ireland manager Mick McCarthy says ‘blah-di-blah’ about a current Irish manager’s decisions."