When ESPN Stats & Information created QBR two seasons ago our goal was to incorporate the context and details from all aspects of quarterback play and translate them into a single number.
To tangibly show what we mean let’s see how QBR compares to the traditional measure of QB play – the NFL passer rating – to see which quarterbacks have relatively large differences in the grades from each system. Passer rating, as you may know, evaluates a quarterback using completions, yards, touchdowns and interceptions on a per attempt basis without adjusting for the game situation.
Andrew Luck: 6th in QBR (71.6), 29th in Passer Rating (76.1)
Luck is the most extreme example of how QBR and passer rating differ. His traditional stats are poor. He’s tied with Drew Brees for the most interceptions in the league, his completion percentage is 32nd among the 34 qualified quarterbacks, and his yards per attempt – arguably the best traditional stat in his resume – is right around league average.
A deeper look at Luck’s play tells a different story. His high interception total and low completions percentage can be largely explained by how far he is throwing the ball in the air. Luck’s average pass attempt travels 10.3 yards downfield, the longest in the league. This not only causes more interceptions, but also means his interceptions are less costly as they are picked off farther from the Colts’ end zone. And, of course, deeper throws lead to bigger plays for the offense when completed.
Most First Downs on Scrambles
2012 NFL Season
Not only that, but Luck has been deadly with his legs. He has rushed for 21 first downs (third most for QBs) and has gotten a first down on a QB-high 48 percent of rushes. He’s been particularly dangerous while scrambling, picking up the most first downs among QBs while having only the fifth-most attempts.
And finally Luck has been at his best when his team needs him the most. On third downs Luck is converting first downs at a well above average rate while gaining 14.7 yards per completion – the best in the league. And we’ve all seen what Luck can do late in close games. He already has five fourth-quarter or OT game-winning drives in his 12 NFL starts.
Philip Rivers: 29th in QBR (39.2), 16th in Passer Rating (85.1)
The reason for Rivers’ higher passer rating is his 65.3 completion percentage, which is eighth in the league and roughly in line with his career average. But the big difference between Rivers this year and in seasons past is where these completions are going. Rivers’ average pass attempt travels seven yards downfield, nearly a yard-and-a-half shorter than in any of the past five seasons.
Another important cause of Rivers’ decline is his increase in sacks. Last season Rivers was in the better half of the league in sacks per dropback, but this year has taken the second-most sacks in the league despite his average time in the pocket staying the same (2.8 seconds per dropback). As generally occurs when a QB is sacked more often, Rivers is fumbling more. He leads the league with 11 fumbles.
And speaking of late game situations, Rivers has been terrible in the fourth quarter or OT of one-score games. His QBR of 3.1 and passer rating of 32.5 are both by far the worst among qualified quarterbacks. However QBR is weighting these situations more; passer rating is not.
Aaron Rodgers: 8th in QBR (69.8), 1st in Passer Rating (105.0)
Rodgers, the NFL leader in passer rating, has a similar profile to Rivers. His 67.4 completion percentage is buoyed by the fact that his average pass travels only 7.7 yards downfield – the 23rd-longest in the NFL. On throws that travel at least 10 yards downfield Rodgers’ completion percentage falls to 51, outside the top 10.
Sacks are also a big problem. Rodgers has taken a league-high 39 despite getting more time in the pocket on his average dropback compared to last season when he ended the season with 36 sacks.