Martinez hints that he may leave Porto
The Colombia international scored 26 times in 30 Primeira Liga matches last season and has seven goals to his name from nine top-flight fixtures this campaign.
Martinez, who joined Porto from Mexican side Chiapas in 2012, has revealed he would welcome a move - the likes of Chelsea and Napoli are said to be interested - if the conditions were right.
"The years are passing and one day I hope to make a good transfer," he told Record.
"It clearly depends on Porto, a club that sells its players so well.
"Leaving or staying depends on Porto, but I will only go if there is something concrete."
While Martinez has 10 goals this season in all competitions, he has not found the back of the net in his last five Porto games.