The Netherlands international has been linked with a move to Goodison Park, with David Moyes reportedly having sent scouts to watch the 21-year-old.
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"I don't know anything about an offer. I'm sure Everton is following me but I don't think about it," he told reporters.
"It's with a reason that I talk with Feyenoord about my contract after this season. I want to finish second and after that I'll think about my future."
Despite his age, the centre-back has captained the Rotterdam side this season and led them to third place in the league behind PSV and Ajax.
Toffees boss Moyes could target the defender as possible partner for his international team-mate Johnny Heitinga. Feyenoord have also rubbished the rumours, however, claiming that no club has made an offer for the player yet.
"No club, including Everton, has made an approach for Stefan," Feyenoord's technical director, Martin van Geel, declared.