In Baseball, Basketball, Football, Hockey, Sports. Comments. The average playing career for an NFL players is 3.5 years, the average MLB career is 5.6 years, the average NBA career is 4.8 years, and the average NHL career is 5.5 years.Playing in one of the major four American sports takes a toll on a person’s body that is nearly unfathomable.omments. The average playing career for an NFL players is 3.5 years, the average MLB career is 5.6 years, the average NBA career is 4.8 years, and the average NHL career is 5.5 years.