The Latics boss believes that the Irish international would some day leave the club but stressed that he currently needed to focus on playing
However, while indicating that the club had received no offers for McCarthy, the former Swansea boss admitted that the 22-year-old Republic of Ireland international would eventually go on to depart the club.
"We will always feel really pleased with compliments towards our players. But James McCarthy is a young man. At 22 he is still developing," said Martinez. "One day he will be challenging to win titles and to be in the highest position in the game, there is no two ways about it."
He added: "But he is still developing and the performance that he had on Saturday (against QPR) shows that he is developing in the right way. The last thing he needs now is to be distracted from his good work and the way he is developing.
"In January, we are not going to do anything else apart from adding players that can help us in becoming a bit stronger," concluded the Wigan boss.