According to widespread reports, City have turned their attentions to McCarthy after being snubbed by Aston Villa captain Fabian Delph. But Martinez, who also coached McCarthy at Wigan, says the 24-year-old is a key member of his side and will remain so.
After watching Everton move into the final of the Barclays Asia Trophy, courtesy of a penalty shootout win over Stoke, Martinez said, when asked about McCarthy: “He’s not for sale.
“My responsibility is to try to keep bringing competition into the squad. I think what we have got now is a very strong competition for places and we don’t want to lose that.
“We are not in a situation at this football club that we have to sell to balance the books. What we want is to be successful and create a winning team.
“James McCarthy has been a top performer in the last few seasons. At the age of 24, to be over 300 games shows the know-how he brings, together with young legs and good energy.
“He is a vital part of our squad.
“It’s important that we keep improving, keep getting stronger and that is the only focus we have – not losing assets.”