Sporting keeper Stojkovic lasts an hour at Everton trial
The Serbia international was expected for a trial spell on Merseyside but stayed barely more than an hour.
"He was at the club on Wednesday but left after only one hour," director of communications Ian Ross told Jornal de Noticias.
"He did not justify anything to anybody.
"He is most probably not going to join us.
"We have been told that he is a complicated character but this surprised us."