A couple of weeks ago, I wrote the differing rookie seasons of Andrew Luck and Robert Griffin III. The numbers still hold — Griffin dominating in all traditional stats, while Luck throwing more passes downfield than any other quarterback — so I sat down with ESPN’s Jeff Bennett to figure out why Luck ranks ahead of Griffin in ESPN’s QBR.

After seven weeks, Robert Griffin III of the Redskins has exceeded even the most optimistic expectations. He leads the N.F.L. with a 70.4 completion percentage, and could become the first rookie to lead the league in that category since Parker Hall with the Rams in 1939.

Griffin also ranks first in yards per attempt with an 8.5 average, and could become the first rookie since another Ram, Bob Waterfield in 1945, to lead the N.F.L. in that statistic. Only two rookies in professional football history have ever led the league in both completion percentage and yards per attempt. The first was another Redskin, Sammy Baugh, in 1937; the last was Greg Cook, in the American Football League in 1969 (his career was ruined by a shoulder injury that year).

Griffin’s statistical domination of the record book has been astounding. And that’s before we get to the fact that he has 468 rushing yards and 6 touchdowns in seven games, putting Cam Newton’s rookie rushing records in both categories (706 and 14) in jeopardy.

Griffin will always be compared to the man selected one spot before him in the 2012 draft, Andrew Luck. And on the surface, there’s no comparison. Luck ranks 32nd in completion percentage (53.6) and 25th in yards per attempt (6.7). Whereas Griffin ranks third in traditional passer rating (101.8) behind Aaron Rodgers and Peyton Manning, Luck is tied with Brandon Weeden (72.3) and ahead of only Matt Cassel for last place.

But traditional statistics don’t always tell the full story, especially when we’re dealing with a sample size that’s smaller than half a season. Those watching Luck have usually come away thinking that he’s the next great quarterback, despite the raw numbers. Fortunately, there’s a way to fill in the rather large gap between perception and statistical production. One of those tools is ESPN’s Total QBR, which ranks Luck as the sixth-best quarterback in the N.F.L. this season. That’s even ahead of Griffin, who is eighth in QBR.

Jeff Bennett of ESPN Stats & Information, in a telephone interview, was able to help explain why Luck was not only the best rookie quarterback this season, but also perhaps the most underrated quarterback in the N.F.L.

Difficulty of Throws

It’s a gross generalization, but Luck plays in a vertical offense while Griffin plays in a horizontal one. Griffin ranks first in completion percentage while Luck ranks 32nd, but that has as much to do with the throws they’re asked to make as each quarterback’s accuracy. Luck‘s average pass attempt has traveled 10.2 yards past the line of scrimmage, the longest average pass distance in the league (this was before “Monday Night Football”; Jay Cutler was second at 9.9 entering the game). Griffin averages 7.9 yards downfield per pass attempt, slightly below the league average of 8.2.

And Luck’s long average pass distance isn’t simply a product of throwing lots of incomplete passes down the field. His average pass distance on completions is 8.6 yards past the line of scrimmage, also highest in the N.F.L. (Cutler was fourth at 8.3 entering Monday night). Griffin’s completions come an average of 5.8 yards from the line of scrimmage, well below the league average of 6.5.

Those numbers agree with Brian Burke’s data at Advanced NFL Stats, which show that Griffin has thrown only 14 percent of his passes 15-plus yards past the line of scrimmage, the lowest rate in the league. Luck has thrown only 11 percent of his passes at or behind the line of scrimmage, while Griffin is in an offense that has let him throw 44 passes at or behind the line, accounting for 23 percent of his attempts. Coach Mike Shanahan and his offensive coordinator, Kyle Shanahan, deserve credit for molding an offense that fits Griffin’s strengths. Unfortunately for Luck, nothing is being made easy for him in Indianapolis.

Yards After the Catch

Casting Luck as a downfield thrower is true, but only half the story. Unlike many rookie quarterbacks, whether through design or lack of talent, Luck rarely has a running back as a checkdown option. According to Footballguys.com, Colts running backs have been targeted on just 7 percent of all Indianapolis passes, the lowest mark in the league. Conversely, Colts receivers have been targeted on 72 percent of Indianapolis attempts, the highest mark in the N.F.L.

In the same vein, much of Griffin’s production has come via yards after the catch. On average, passers in 2012 have gained 56 percent of their yards through the air and 44 percent on yards after the catch by their receivers. For Griffin, 51.4 percent of his yards have come via his receivers after the catch, the fifth-highest mark in the league. Luck, in large part because of his downfield passing, has gained 68.9 percent of his yards through the air, the highest percentage in the league, and therefore has been helped the least in terms of yards after the catch.

However, simply putting the stats in this context does not mean that Luck has been a better passer than Griffin; rather, it is to simply close the extraordinary gap created by traditional statistics. Griffin’s completion percentage and yards per attempt average are still more impressive even after adjusting for the difficulty of his throws. If we looked simply at their passing numbers, even ESPN’s Total QBR would rank Griffin ahead of Luck, by a score of 68.7 to 60.7. And while you know there is more to being a quarterback than just passing, you might be surprised to learn that looking at those things actually vaults Luck ahead of Griffin.

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