The 27-year-old striker, who spent last season on loan at Estudiantes, has yet to live up to his £6.5 million price tag since moving to the DW Stadium in June 2010
The Argentine has failed to live up to his £6.5 million price tag since moving to the DW Stadium in 2010 and spent last year on loan with Estudiantes.
However, the Latics boss has backed the 27-year-old striker to play a big part for the Greater Manchester side this term.
Martinez told reporters: "When he came back Mauro made his views very clear that he wanted to be successful with Wigan Athletic.
"He's been working really well and we've got very strong competition in those forward positions. Mauro's attitude has been tremendous.
"He wants to play games, he wants to be ready to help the team, and that's a real sign of maturity. Over the course of the season, he's going to be very important."
The Spanish manager went on to lament the refereeing decisions which have gone against his side in recent games, such as the penalty awarded to Danny Welbeck last weekend at Old Trafford following minimal contact in the box.
He said: "It's true you look at the incidents and you analyse the games and just by the law of averages you should get wrong decisions going your way, and sometimes it's difficult to understand that you don't get that.
"All you want is bad calls balancing out, so from that point of view it's just the disappointment that two or three games in a row against certain teams you don't get what you feel you should.
"But it's not good to keep talking about refereeing decisions because that's not going to get us points."