The 19-year-old was recalled to the first-team squad last month to provide cover for injuries following a loan spell at Championship side Cardiff.

However, the midfielder has now been added to manager Alan Pardew's injury list.

"I can confirm that Vukic is out for the season - he injured his knee," said Kavcic, who is preparing his squad to face Mata Under-21s next month.

"What can we do? Nothing, we will have to find a replacement for him. But of course it won't be easy, he is a great player and a leader of our team."