Baugh about to complete a pass, probably.
Let’s take completion percentage. The passer rating formula measures completion percentage by taking a passer’s completion percentage, subtracting 30%, and multiplying the result by five. This made sense when the average completion percentage was around 50%; in that case, 50% minus 30% equals 20%, and multiplying that by 5 gives a result of 1.00.
To adjust for era, we replace “30%” in that formula with “league average minus 20%.” So in 2018, the league average completion percentage was 64.9%, which means we would use 44.9% for this formula. Drew Brees completed 74.4% of his passes; if we subtract the baseline from his result, we get 29.5%. Multiply that result by 5, and Brees gets a completion percentage score of 1.48 for 2018.
If we do this for every quarterback in every season of his career, and then weight each season by his number of pass attempts, we can get career grades. This is one way to come up with career completion percentages adjusted for era.
The overwhelming champion in this regard is Sammy Baugh, who led the NFL in completion percentage 8 times during the decade of the ’40s. As recently as 1975, Baugh was still 4th all-time in career completion percentage, and less than 1% off of the leader. Baugh has a rating of 1.58, which means on average he was better at completing passes relative to his era than Brees was in 2018.
The top passers in measuring completion percentage this way are Baugh followed by a who’s who of the completion percentage kings: Len Dawson, Otto Graham, Steve Young, Joe Montana, Sid Luckman, and Drew Brees.
The bottom 5? Rex Grossman, Jay Schroeder, Doug Williams, Mike Pagel, and the man at the very bottom of the list is… Derek Anderson.
The table below shows the 189 passers with 1,500 career pass attempts. Here’s how to read the table below: Baugh has the best adjusted completion percentage, and he threw 2,995 career attempts. He played from 1937 to 1952, and has an era-adjusted passer rating of 92, which ranks 3rd. He has a completion percentage grade of 1.58. The final column? That shows Baugh’s completion percentage grade relative to the other 3 variables in the passer rating formula (Y/A, TD%, and INT%). So Baugh is +0.27 better in completion percentage than the other 3 metrics, on average.
In some ways, it’s that last column that is most interesting to me. Completion percentage is significantly overstated in the passer rating formula, so if a player is much higher in completion percentage than in their average of the other three metrics, it’s very likely that passer rating overstates their true value. So let’s break the groups into those whose passer ratings are inflated by strong completion percentages and those whose ratings are deflated by weak completion percentages.
Boosted By High Completion Percentages
Frank Tripucka is your leader here, followed by Sammy Baugh, Ken Stabler, Chad Pennington, Troy Aikman, Brian Griese, Bart Starr, Drew Brees, Tim Couch, and John Brodie. It’s an interesting group of players: Tripucka and Couch still have below-average passer ratings (66.7 is average) despite strong completion percentages, while Griese, Brodie, and Aikman were basically average other than their stellar completion percentages. Meanwhile, Stabler and Pennington were efficient passers who happened to be best at completion percentage, and that goes triple for guys like Baugh, Brees, and Starr. Pennington was a very good quarterback, but his 29th-place ranking in passer rating is more a function of how the formula tips the scales in favor of high completion percentage.
Harmed By Low Completion Percentages
Doug Williams is the biggest outlier here, and he had a very low sack rate which helps to explain his low completion percentage. Other players who were much better in Y/A, TD%, and INT% than completion percentage include Jay Schroeder, Michael Vick, Derek Anderson, Frank Ryan, Daryle Lamonica, Colin Kaepernick, Aaron Brooks, Don Meredith, Mike Pagel, and Terry Bradshaw.
Vick is another interesting choice. Did you know that from 2001 to 2013 he led all players in yards per completion but he ranked 46th out of 50 passers in completion percentage? Vick also replaced a lot of easy, 5-yard completions with 5-yard scrambles (or longer), which artificially deflated his completion percentage. Some of that probably applies to Colin Kaepernick, too, and his case is even more interesting because of his remarkably low interception rate juxtaposed against his low completion percentage. Lamonica and Ryan were two HOF caliber passers who are underrated when you examine completion percentage: how much differently would we view their careers if they had slightly lower Y/C averages and higher completion percentages?
What stands out to you?
