If you don’t follow Brad Congelio, PhD and Professor of Sports Analytics at Kutztown University (@BradCongelio), you should – lot of great sports analytics. A tweet of his got me thinking on different metrics for offensive line, including PFF grades and ESPN’s win rates, and I wanted to look at a comparison of them.
Pass and run block PFF grades
First, a scatter of PFF run (x axis) and pass (y axis) grades. Top right are teams graded highly in both, bottom left are team graded poorly in both. Bottom right are teams with good run block grades but poor pass block grades and top left are teams with good pass block grades but poor run block grades.
Pass and run block win rates
Next, the same scatter of teams but using ESPN’s run block win rates (x axis) and pass block win rates (y axis). Pass block win rate measures when an offensive lineman holds their block for at least 2.5 seconds. Run block win rate is a bit more complicated and measures various outcomes like disrupting the running lane, forcing a change in running lane, and a tackle within 3 yards of the line of scrimmage. For more information, go the ESPN’s write-up here.
Differences Between PFF and ESPN OL Win Rates
And lastly, a view on the differences between PFF grades and ESPN’s win rates.
Many people hate on PFF’s grades which I think is misguided – I believe they are largely right but will, like all metrics trying to capture a complicated sport like football, miss out on things. The one that stuck out to me was Pittsburgh which is one of the biggest outliers between the data sets. I am an Eagles fan but lived in Pittsburgh for twenty years and have always liked the team. Also, I had the Steelers pick in Brand Lee Gowton’s 2021 fan-led mock at Bleeding Green Nation – I took tackle Samuel Cosmi and thought the Steelers inevitably taking one of the running backs was going to be a huge mistake because their issues are the offensive line.
Pittsburgh’s pass block grading rated really well on PFF (4th in the league) but it is really a factor of Roethlisberger getting rid of the ball at a historically quick pace – in 2020, he averaged 2.17 seconds to throw, by far quickest in the league. This resulted in a plodding offense and watching any tape, the line was just awful last year when they needed to be.
A commenter on Brad Congelio’s tweet also questioned Kansas City’s run blocking, which is another that shows a difference between PFF grades and OL win rates. One thing that stands out to me with Kansas City is the amount of run success that came from Mahomes and Tyreek Hill – they combined for 24% of rushing yards and elevated YPC. Removing Hill and Mahomes and Kansas City’s YPC would be 3.39, putting them near the bottom of the league. Rushing yards are rushing yards, so it isn’t valid to just exclude rushes by non-running backs, but it does point to why one metric scores out differently than another and why watching the Chiefs didn’t feel like watching a strong rushing team.
Code for this quick analysis is in the following GitHub repo: