The former Estudiantes and Boca Juniors star arrived at Wigan in the summer with a reputation as one of South America's top goal scorers.
But he has yet to find the net and is now being eyed by Bari and other foreign clubs.
Martinez said: "As an asset he is 25 and has scored 50 goals in the last two seasons for Estudiantes.
"But it's not about making money. We want Mauro here. The work now is for us to adapt to Mauro and for him to adapt to the British game.
"He is not at the end of his career and he's not scoring because his legs are gone.
"It is a football puzzle we have in our hands and we have to put it together.
"But we are not far away to finding the solution."