McCarthy scored twice in Wigan's weekend win over Blackburn
Wigan manager Roberto Martinez says midfielder James McCarthy faces a "very, very deep" decision to make over his international future.
Glasgow-born McCarthy has played for the Republic of Ireland but not yet in a competitive international.
And speculation has suggested he could switch allegiance to Scotland.
"I do not know if it is a decision for him to make now or not. We need to give him plenty of time. We need to respect him," said Martinez.
The Wigan manager added: "He wants to help Wigan. For me that is fantastic. It (international football) is something he needs to think about with his family, with his friends.
"It is something very, very deep. But I do not think he has focused on that at all, although it is great to have two nations fighting over you.
I would have him playing for Scotland every day of the week but it is up to him. He is a top midfielder and the more who come in to the Scotland squad the better
McCarthy's Wigan team-mate James McArthur
"James is probably the most mature 20-year-old in football; it is a compliment to him. I don't think it is going to affect him. It is going to give him a more arrogant feeling if you want."
McCarthy withdrew late from the Republic of Ireland squad that took on Wales on Tuesday.
"It wasn't the right time for him to go," added Martinez. He could not have coped with the physical demands. That's it really.
"I spoke with the Republic of Ireland staff to make sure they knew the programme James was on.
"When James got injured late in October he was so disappointed he just wanted to get back fully fit as quick as a he could. He told me then he needed to forget his international career and that was the conversation we had.
"If you look at his performance on Saturday, James McCarthy is going to be one of the top footballers in Europe. What a player to have for your country or club."
Scotland head coach Craig Levein has refused to be drawn on the possibility of McCarthy performing an international switch.
"I don't want to speak about it," Levein said after Scotland's 3-0 win over Northern Ireland.
"This should be about recognising the efforts of the players that played for Scotland tonight (against Northern Ireland).
"Other stuff I can talk about when we are away from a match situation.
"This is for talking about the players who played for Scotland tonight."
Republic of Ireland coach Giovanni Trapattoni insisted the 20-year-old is still in his plans after the player withdrew from the squad to face Wales on Tuesday.
"All Irish players are in our future," said the Italian.
"We look at the new young players and McCarthy can play in the future."
McCarthy's Wigan team-mate James McArthur says he would like to see his fellow Hamilton youth graduate join him in the Scotland squad.
"I don't really know anything about it," said McArthur after scoring in the Scots victory against Northern Ireland.
"All I know is that he picked up an ankle injury after getting a kick on it. I was led to believe that is why he wasn't in the Republic of Ireland squad.
"But you never know, things happen behind the scenes that you don't know about.
"I have spoken to him about it many times but I can't really comment on it, it is James' decision. You would need so speak to him.
"I would have him playing for Scotland every day of the week but it is up to him.
"He is a top midfielder and the more who come in to the Scotland squad the better."