The Italian's five-year tenure with the Green Army came to an end earlier today following the failure to qualify for next year's World Cup in Brazil, which was preceded by a disappointing Euro 2012 campaign.
McCarthy, who was handed his first cap in a friendly against Brazil in 2010, said that the players always enjoyed working with the 74-year-old, who allowed him extra leave to complete a deadline-day move to Goodison Park.
"He stuck by me, gave me my chance and has been good for my career, so I'm disappointed to see him go," the 22-year-old told reporters. "I'm gutted, to be honest.
"It's just one of those things. The FAI have had a meeting today and decided it's the time for him to go. Like I say, it's disappointing because the players enjoyed working with him.
"When I spoke to him last week it said it was no bother to report on the Tuesday morning first thing. He said hopefully everything would work out [with the move to Everton] and thankfully it did. I'm grateful that he allowed that to happen."
McCarthy has 18 caps for Ireland.