Martinez would still love to keep his explosive hitman but is well aware that Tottenham and Liverpool will come calling with £15million cheques in the summer.
He said: "Sometimes we forget that he's only 21. The potential is incredible. From technical and tactical aspects he's improved a lot.
"But there's still a long way to go. His potential is so huge, he can go as high as he wants to. You can't stop players moving as long as the club gets a fair price. It would be unrealistic of us to think we're not going to lose players.
"But it's important the players give everything they have got for Wigan and then when the time arrives the chairman will never stop anyone from moving on if they want to."