The and the NFL began handing out a Defensive Player of the Year award in 1971, and none too soon. The league MVP award had been introduced in 1957 (known for the first four years as the "Most Outstanding Player"), and in each of its first 14 years it went to a quarterback or a running back. Essentially, the new award in 1971 was a much-needed acknowledgement that there are MVP-level performances on the defensive side of the ball, too.
(Ironically, the first Defensive Player of the Year, Minnesota DT Alan Page in '71, was also the first defender to win overall MVP.