The Belgian is most known in the Premier League as an attacking, goalscoring midfielder – and it was in that position that he most often played for Everton, particuarly following the sale of Tim Cahill in July 2012.
However, the 25-year-old told the latest edition of Four Four Two magazine that he feels more comfortable playing further back.
"As a young player I played up front, on the wing, in midfield and when I started in the reserves at Standard Liege I played centre-back," he admits.
"It was a good position for me because I am tall and good in the air, but I can also pass the ball. Maybe it's a position for me in the future?
"My best position is defensive midfield. During the last few years with David Moyes I played further forward and I scored some important goals, which is why he kept me there and I liked it because I was young and learning."
Moyes and Fellaini were reunited on transfer deadline day when the new Manchester United manager signed him from former club Everton for £27.5 million.