Away from the game he is a diamond jewellery trader, designing and selling sparkling pieces to a string of top sports stars and celebrities.
McCarthy, 23, told The Sun: "As I was growing up there were stories about players getting side-tracked by gambling due to the amount of spare time they get.
"My dad was adamant he didn't want me going down that route. Adam was already working in the diamond trade so we sat down and had a chat as I wanted to get involved. And he allowed me this opportunity to go into business with him.
"Not only does it keep me occupied outside of football, it's something I've a genuine passion for.
"I help with the design ideas and also go to a lot of meetings with Adam after training.
"We've developed a great reputation. As a footballer, I have contacts and a lot of players are our clientele.
"Players will be sat in the dressing room and come in with a new piece of jewellery and the lads get talking.
"Often their wives, girlfriends or relatives want a piece and we give them advice on the right watches, jewellery or stones to buy or design something unique for them.
"I've designed many different pieces, including our latest range of bracelets that have been launched. We make everything from engagement rings to ear-rings and from cufflinks to watches."