When Dan Marino became the first NFL player to throw for over 5,000 yards in 1984, it was certainly a big deal and solidified the 23-year-old quarterback as a superstar who could change how the position was played. Of course, if there had been a 17-game season five years prior, Marino may not have been the first QB to throw for 5,000 yards as Dan Fouts could have easily gotten there.
Twice.
Fouts threw for 4,715 yards over 16 games in 1980 and 4,802 yards over 16 games in 1981. Marino threw for 5,084 yards in 1984, which of course meant that he may have topped 5,400 yards if he had a 17-game season to work under.