The Republic of Ireland suffered a 3-0 defeat to Belgium at the ongoing 2016 European Championship in France last weekend.
McCarthy featured in the Group E game at Nouveau Stade de Bordeaux in Bordeaux, and he did not play well.
The 25-year-old former Wigan Athletic midfielder could have done better on Belgium’s second goal of the match.
Full-back Thomas Meunier swung in a cross into the Republic of Ireland penalty box, and midfielder Axel Witsel headed home from close range, with McCarthy caught ball-watching.
The Everton man, who was also responsible for another of Belgium’s goals against the Republic of Ireland last weekend, has explained how he got over his mistakes.
“My performance against Belgium wasn’t acceptable and I knew that,” McCarthy told The Scottish Sun. “It wasn’t good enough.
“Afterwards I felt completely gutted but I had people there for me. My family were constantly on the phone, making sure everything was fine. My team-mates were there for me along with the management. They all stuck by me.
“I spoke to Jamsey (James McArthur) earlier in the day, we’re in touch all the time. Big Easty was another one who was there for me along with my family and team-mates here.”
McCarthy redeemed himself on Wednesday, as he helped the Republic of Ireland to a famous 1-0 victory over Italy in their final Group E game.
The victory meant that Martin O’Neill's side progressed to the last-16 stage of the Euro 2016 finals where they will take on home nation France.