While nothing has been confirmed, Martinez is expected to join Atletico during next month's winter market.
The striker scored in victory over Gimnasia La Plata on the weekend and again talked up the prospect of moving to Atletico.
"(Diego) Simeone is a great coach, who praises me and speaks well of me, of what I am doing, but I will continue working," he said.
Martinez also hopes his new status catches the eye of Argentina coach Jorge Sampaoli.
He added: "I work to improve myself and I hope I have an opportunity."