The Republic of Ireland international has been in impressive form for Wigan this term, scoring twice in a 2-2 draw with Queens Park Rangers last weekend.
The Latics have previously allowed exciting talents, such as Antonio Valencia and Victor Moses, to leave the club after impressive spells at the DW Stadium.
Martínez believes McCarthy has the potential to excel at any club regardless of stature – but for now the Wigan boss is keen to keep hold of the 22-year-old.
“James McCarthy’s got the potential to play anywhere in the world and whenever he’s ready we’ll never stop him,” Martínez told Wigan Evening Post.
“But James McCarthy is at a very good club now and we want top players to stay here for as long as we can.”
“At 22 to have the tactical awareness that he has and to be so consistent week in, week out…
“James knows he needs another period of improvement, but from a technical point of view he can play in any team in the world and he will do one day.
“We just enjoy seeing him grow and seeing him enjoy his football and being an important player for us and at international level.”