It's one of those bizarre twists of fate in football that McCarthy is a vastly experienced player at club level, but a rookie on the international stage. There are signs that could change as manager Giovanni Trapattoni has talked up McCarthy ahead of the Greece game, now his big chance to establish himself in the side at last, two and a half years after his senior debut.
"I have only played a few games for the Irish senior team but I have five games in a row now and it's great to be getting games under my belt," McCarthy told the Herald.
"I am trying to take it one game at a time, but hopefully the longer a run in the team goes on the more you get used to the system we play with Ireland, and everything starts to click.
"Since I was a kid all I wanted to do was play football, and hopefully I can kick on now. Every player at every level wants to be in the starting XI and I'm no different, I want to play as many games as I can for my club and my country and I'd love to get a chance against Greece this week.
"I love playing international football, I have enjoyed every minute of it so far and if I get to play on Wednesday and again against Poland in February, it would be a dream come true to get into the team for the big matches against Sweden and Austria.
"I am enjoying the fact of being in the team with Ireland now but I won't get frustrated. I will keep working hard and get as many caps under my belt as I can."
McCarthy's dedication to the cause is unquestioned: even when he was - unfairly - dismissed by Trapattoni and sent off to play for the Irish U21s as recently as last year, he always turned up, unlike fellow pros like David Bentley who refused to turn up for U21 duty with England as it was beneath him.
"I was happy to play for the U-21s, I got on well with everyone in the squad and the staff. I would never say that I was too big for the U-21s. I didn't even consider knocking back the U-21s, I'm not like that. The important thing for me is to play for any of the international squads."
And international success is relative. While in Dublin for media duties yesterday ahead of the game against Greece, McCarthy took a trip down memory lane when asked to recall his first involvement with the Republic, an U-17 friendly against Italy in Dublin way back in January 2007.
The game was a success, a 1-0 win for Ireland, but success did not come for McCarthy's team-mates. Of the Irish side that day, McCarthy is the only one with a senior cap and, apart from him, the only member of the U-17 side still playing at a high level abroad is Huddersfield striker Sean Scannell.
A few more are enjoying a good League of Ireland career (Conor McCormack and Shane O'Connor at Shamrock Rovers, Gareth Matthews at Shels, Eric Foley at Drogheda) but the majority of McCarthy's ex-team mates are either playing non-league football in England with clubs like Lewes (Kieron Thorp), Bromley (Ian Daly) and Billingham Town (James Cronesberry) or have quit soccer, some to concentrate on GAA (David Joyce with Mayo, Paul Honohan with Cork's U21s).
"It's a shame to see so many of those guys gone from the game," McCarthy reflected.
"I thought Ian Daly, who was at Man City at the time, was a different class and I was sure he'd make it. I played in midfield with Conor McCormack and again I thought he'd go very far, but it's a tough game. You need to get a break along the way. I got a break by getting into the Hamilton team and then getting a break again with a manager down south (Roberto Martinez) who gave me a chance as well. You need a bit of luck and I'm fortunate to have had that bit of luck. It's a crazy game, you can never take things for granted. One minute you're at a big club and have high hopes and the next minute you're at the bottom. It's a cruel business and I feel fortunate to be where I am."
The good fortune of having an international career is something that crops up regularly for McCarthy as his club manager, Martinez, was never capped. "He's fascinated by international football and he's always asking about the Ireland set-up, how I am enjoying it and how I do in the games," says McCarthy.
A keen Celtic fan, McCarthy was due to be in Parkhead for last week's thriller against Barcelona and even had a ticket but was unable to go due to club duties. That win for the Bhoys has put Irish reaction to the 6-1 defeat to Germany under the spotlight, especially the theory put forward by the Ireland manager and some players that Ireland didn't stand a chance against the Germans as the opposition were just too strong - not a view taken by Celtic who took Barcelona by the scruff of the neck.
"Celtic got a result against Barcelona, one of the best teams in the world in my book, and you look at Germany, one of the best football countries in the world, but it will always be tough," he says.
"If you look back at the Barca game, Celtic rode their luck at times and the keeper pulled off a lot of great saves at Parkhead. Germany were unstoppable the night we played them. Every chance they had seemed to go in and it's frustrating.
"We just have to try and take the positives out of the Faroes game and go into the Greek game to get a result to build ahead of the qualifiers in March."