livestrong.com just 2.57 years average career length source Studie expectancy shortest career spans 3 years with the shortest average career length http://www.livestrong.com/article/15...er-nfl-player/ http://www.livestrong.com/article/15...er-nfl-player/ average career is 3.3 years http://www.livestrong.com/article/15...er-nfl-player/ Livestrong.com average career NFL Player’s Association 2.57 years http://www.livestrong.com/article/15...er-nfl-player/ expectancy http://www.livestrong.com/article/15...er-nfl-player/ livestrong.com average career for running backs h/t Livestrong http://www.livestrong.com/article/15…er-nfl-player/ http://www.livestrong.com/article/15...er-nfl-player/ shortest of any position average career is 3.3 years just 2.57 years