Wolves have released goalkeeper Marcus Hahnemann.
The American comes off contract at the end of the month.
"Marcus has been fantastic for us over the last two seasons - both in his performances on the pitch and his influence off it," McCarthy told the club's official website.
"When we brought him in we knew we were getting a very good experienced keeper to push Wayne Hennessey all the way for the first-team shirt.
"And when the time came for him to get his opportunity he made the most of it and played a key role in helping us stay in the Premier League.
"Even when he then lost his place to Wayne last season, he remained supportive and professional and helped in Wayne's development both as a player and as a person.
"With his enthusiasm and personality, not to mention some very different hobbies and interests, Marcus was a great character to have around the place and hugely influential in the dressing room.
"It was a pleasure for all of us to have him in the squad for the last two years, and we wish him all the very best for the next stage of his career."