Dak Prescott has been a historically great rookie (so far)

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Dallas Cowboys rookie quarterback Dak Prescott is having a phenomenal season by almost any measure. How does it compare to other great rookie campaigns?

It's difficult to compare quarterbacks from different eras for two primary reasons. First, not all of the official statistics of the modern era were always kept; for example, sacks weren't officially recorded until 1982. Second, passing has varied significantly throughout the years, so stats such as the traditional passer rating are fairly meaningless when comparing a player from 2016 to one from 1970.

We do have a few common measures of quarterback performance we can rely on to compare passers across eras. Total yards, pass attempts and interceptions can all be boiled down into a stat known as adjusted yards per attempt (AYPA). Yards per attempt is one of the best ways to measure quarterback play because it's a rate stat that's highly predictive of winning games. The "adjusted" part subtracts 45 yards from the yardage total for every interception a quarterback throws before dividing by attempts; the 45-yard adjustment has been shown to be roughly the yardage equivalent of an interception.

To remedy the problem of different passing environments across eras, we can compare each quarterback's AYPA with the league average for that season. For example, Prescott's AYPA is 9.2 so far this season, while the league average is currently 7.2. That means Prescott exceeds the league average by a net of 2.0 AYPA.

Only three other rookie quarterbacks in NFL history with as many starts as Prescott have exceeded the league average in AYPA for their respective seasons by more than that. Otto Graham blew the doors off the rest of the league in 1946, averaging 11.2 AYPA when the rest of the league passed at a measly 3.7 AYPA rate. Y.A. Tittle averaged 8.4 AYPA as a rookie in 1948, compared to a league average of 4.6 AYPA. The third quarterback to top Prescott on the list is lesser-known Greg Cook of the Bengals, whose 1969 season beat the league average by 2.6 AYPA. Cook's career was cut tragically short by a chronic shoulder injury.

The following is the list of rookie quarterbacks' with the best AYPAs when compared to the league average of their respective years:

Prescott's passing performance through 10 games outshines the season-adjusted rookie averages of other great first-year quarterbacks Dan Marino, Russell Wilson, Matt Ryan, Jim Plunkett and Ben Roethlisberger. He even beats "non-rookie" rookies, like Jim Kelley and Warren Moon, who had experience playing in the USFL and CFL respectively.