The Netherlands international has only made eight league starts this season, with Toffees boss David Moyes favouring Phil Jagielka and Sylvain Distin in the centre of his defence in recent weeks.
It is a far cry from seven months ago, when the 29-year-old picked up the club's player of the season award and there were rumours earlier in the season that he was close to signing a new deal at Goodison Park.
However, with the January transfer window rapidly approaching Heitinga's agent Rob Jansen confirmed the defender is not happy with his current situation at the club.
Turkish side Fenerbahce were one of the sides linked with a move for Heitinga in the summer and Jansen admits the player would seriously consider any offers that come in.
"Heitinga is definitely not happy with what it happening at Everton and we don't hide that," he told Dutch radio station VI Radio.
"He is looking at a solution. When an appropriate situation arises for a transfer, we will certainly not ignore it."