It wasn't until Rehn attended Immanuel College (Australia) that he believed he could play league football.
At 19 Rehn started his AFL career in 1991 with the Adelaide Crows in their inaugural year in the Australian Football League.
Throughout his whole career at both Adelaide and Hawthorn, Rehn wore the #52 guernsey, and holds the record for the most games wearing that number.
In 2010, Rehn coached the Byron Bay Magpies under-14 side in the Northern Rivers League.
[4] In 2011 Rehn coached South Australia in the 2011 State of Origin Slowdown to a 17.10 (112) to 17.9 (111) victory over Victoria in a charity match at the Adelaide Oval for the Little Heroes Foundation and the Reach Foundation youth charities started by former Melbourne ruckman and 1991 Brownlow Meadallist Jim Stynes.