The Serbia international stopper only joined Sporting last summer, but after a bright start to his career at the Estadio Jose Alvalade, he has struggled to hold down a regular first-team spot.
Sporting are understood to be willing to discuss a potential deal for the 24-year-old, but admit that they are yet to receive a formal approach.
"Contact has been made but we have not yet had any offers," said a club director.
Stojkovic has also revealed that he would be open to a move to the Premier League, but is unsure as to what the future may hold.
"I will not rule out the possibility of going to England," he told Radio Renaiscenca.
"But to find out the truth it would be best to speak with my club."