Duffner was born and raised in the Washington, D.C. suburb of Annandale, Virginia; he played tackle for legendary coach Bob Hardage at powerhouse Annandale High School and played collegiately at the College of William and Mary, recruited to the school by assistant coach Bobby Ross.
This was due to the implementation of his run and shoot offense and quarterbacks John Kaleo, Scott Milanovich, and Brian Cummings.
However, his teams were notoriously weak on defense, frequently giving up points so fast that even his prolific offense couldn't keep up.
After leaving Maryland, Duffner became an assistant with the Cincinnati Bengals from 1997 to 2002, where he served as linebackers coach and then defensive coordinator.
[5] The surname Duffner originates from the German habitational name for someone from Teufen in Württemberg or from Tüffen near Saint Gallen, in Switzerland.