But Martinez is desperate to keep him at the club until the end of the season.
Sunderland are reportedly leading the chase for the Honduras international.
Martinez said: “He’ll probably go next summer, but until then we will go on enjoying his defending and his magical goals.
“Obviously we don’t want to lose our best performers and Maynor has been outstanding the whole season. And it is not just that, he is terrific character.
“He is the kind of player we want to keep. We know that we will not be able to keep him forever because the reality is he is slowly fulfilling his potential, and his potential should be to go to the top of the top.
“He’s got the World Cup in front of him so I don’t think change would be a good decision before such a big event in his career.”