According to a recent NFL Management Council analysis of players who entered the NFL between 1993 and 2002, the average career length for a player who is on his club’s opening-day roster as a rookie is 6.0 years.
The Average for all skaters is 5+ seasons
of course if I am not mistaken NHL season is a little longer and they may play a few more games a season than the NFL (sarcastic remark)
NHL: 5 seasons X regular season games(82) + Playoff Games +410 games
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NFL: 6 seasons X regular season games(16) + playoff games +96 games
NFL looks to be 4X harder on the body