The 22-year-old Latics midfielder will win his seventh successive senior international cap in Wednesday night's match in Dublin, and will do so in a team which will include debutant Connor Sammon and defender Greg Cunningham, who has returned to contention after injury.
McCarthy, James McClean, Seamus Coleman and Robbie Brady have all established themselves as regulars in Giovanni Trapattoni's squad in recent times with the 73-year-old having turned in part to youth in the wake of a disappointing Euro 2012 finals campaign.
But while some of the new boys will have to wait patiently, McCarthy appears to have played himself into contention for a starting berth. And with two vital World Cup qualifiers coming up next month in which the damage of a 6-1 home defeat by Germany needs to be repaired, he knows exactly what is at stake.
He said: "We need to try to put it (the negativity which surrounded the Germany game) to the back of our heads and try to really kick on now. We have got a friendly against Poland, which is not going to be easy.
"It's a good test for us and then next month, we have got the two qualifiers, and we need to go into those games and try to be as positive as we can.
"It's not going to be easy. Sweden and Austria are two massive games and two tough games. They could make or break the group, to be honest."
Trapattoni's hand has been forced in part by the retirements from international football of Shay Given and Damien Duff and injuries to senior men Richard Dunne, Sean St Ledger and Keith Andrews.
However, even a man of McCarthy's tender years knows how important it is to retain the vast experience which is at the manager's disposal when all his players are fit.
He said: "It's always good to see the young boys coming through, but obviously the gaffer can't just blood all his youngsters at the same time.
"We have still got the experienced pros in the squad and we always need that to help us and back it up."
It is a measure of McCarthy's quality that he has already made more than 100 Barclays Premier League appearances for the Latics since his move south from Hamilton in July 2009.
The confidence placed in him by manager Roberto Martinez has paid dividends, and he has taken that on to the international stage.
Asked if he could have expected to have played so much top-flight football by this stage in his career, McCarthy said: "No, definitely not.
"I have worked hard and it's down to the gaffer giving me my chance at Wigan. He believed in me at a young age and he paid money to Hamilton.
"He's been brilliant for me since I went to the club. He's always believed in me and he's always given me my chance, and I am just happy to be part of that.
"It's a dream come true to go and play in the Premier League, to be honest."
Such has been McCarthy's form that he has been linked with a series of potential suitors with Arsenal among them during the most recent flurry of rumours.
However, he remains relaxed about his immediate future.
He said: "It's always good to see your name linked with big clubs, but I am a Wigan Athletic player. I will just keep working hard and if something comes up, then something comes up.
"But at this moment in time, I am happy to keep learning my trade at Wigan.
"Obviously, you want to play at the top level, but I am happy at Wigan just now and we just need to see what the next six months brings us."