FiveThirtyEight.com published a feature this week about Randall Cunningham's legacy in the NFL, and how it set the stage for an era of dual-threat quarterbacks like Michael Vick, Robert Griffin III, Cam Newton and Russell Wilson.

As good as those players are, FiveThirtyEight's Neil Paine ran some statistical calculations which proved that none of them had a single season better than Cunningham's for the Eagles in 1990.

(Excluding the important statistic of Super Bowl trophies won, that is. But you get the idea.)

Using a statistic called Yards Above Backup Quarterback - think of it as an equivalent to baseball's Wins Above Replacement or Football Outsiders' Yards Above Replacement - Paine reached this conclusion about Cunningham's legacy:

In 1988, he piled up 336 YABQ through the air and 171 on the ground, the first time in league history that combination had ever been achieved. In a "down" 1989 season, he notched 248/147, a combo that had only been reached twice before (by Landry in '72 and Cunningham himself in 1988).

And in 1990, Cunningham set a standard for dual-threat seasons that has yet to be eclipsed in the 26 years since. That year, he was 750 yards better than a backup through the air, and he tacked on another 249 YABQ on the ground; if we take the harmonic mean of those two numbers (a particular kind of average that emphasizes high values in all numbers being averaged, in order to capture seasons when a player produced a lot of passing and rushing value), it's the single best combined passing-rushing season by a QB in the Super Bowl era.

Check out all the stats and more on Cunningham's career here.