The 23-year-old has scored four goals in 21 Premier League appearances for the Latics this season, but could leave the club when his contract expires in the summer.
Liverpool manager Brendan Rodgers was linked with a move for the former Chelsea man in December, but Martínez wants to keep the striker at Wigan.
“All I’m focusing on with Franco is that he keeps developing, that he keeps fulfilling his potential and just having the impact that he has today,” said Martinez.
“We will lose players and have to move players on but we also want to keep players.
“I think the window is fantastic for the fans, for the media. It brings great speculation.
“All the fans get excited. It gives you the opportunity to have a second life if you want, in the season. What I hate is that the window is open while the games are going on and I always found it impossible for the players.
“We forget that players are human beings and if you’re going to consider the next move in your career, you’re allowed to do that because as a human being in any job you need to do that.
“The problem is that when you do that while the games are going on, it’s disrespectful to the club, it’s disrespectful to the fans and disrespectful to the competition itself.”
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