Career
Van der Vlag was part of the youth setup at amateur team, v.v. Wildervank, before turning professional with BV Veendam in the Dutch Eerste Divisie in 1997. He played 145 games for Veendam before moving to Go Ahead Eagles in 2003.
After playing for Cambuur Leeuwarden between 2004 and 2009, Van der Vlag returned to his first professional club, Veendam, in 2009.
On July 2011 he re-joined his Veendam head coach Joop Gall by returning at his old club Go Ahead Eagles. In the summer of 2012 Van der Vlag signed with Football Club Emmen.
He left after two seasons to become second goalkeeper of Eredivisie side Football Club Groningen.