The 38-year-old, who has yet to feature this season due to a broken thumb, admitted that while he felt as fit as ever, the inevitable end of his career was nearing.
“I've said for a few years that it sometimes may be my last season,” Van der Sar said, according to The Daily Mail.
“Six months before my contract with Manchester United ended in December 2006, we extended for one year and so far it has been the same every time.
“I wait each season to see where I stand, if everyone is happy and if I can still get motivated. But I know, because I always get older, it is increasingly likely that this will be my last season.
“In December, it will be clear how it goes. By then, I'll have clarity. It is a horrible dilemma. On the one hand I do not oversleep, I feel as good as a few years ago.”
United manager Sir Alex Ferguson has said previously that he did not expect the Dutch 'keeper to continue beyond 2010 - but he may be hoping to be proven wrong, given Ben Foster's recent efforts between the sticks.