Things I Learned From the New PFR Play Finder: Which Teams Chewed Up the Most Rushing Yards by Half?
Posted by Neil on September 4, 2012
One old football aphorism was always that teams needed to "establish the run" -- running early, as the theory went, would set up the pass later in the game. Often it was cited that "Team X is 10-1 when they run 30 or more times in a game," or some such number that failed to see the difference between correlation and causation.
Later, researchers like Football Outsiders' Aaron Schatz would point out that teams have such great records when they rush so frequently because the running game is used to run out the clock late in games by the team in the lead. Teams run when they win, not win when they run.
Using our new Play Finder tool, you can illustrate this by looking at rushing yards by half. Here were the teams who had the most rushing success in the first halves of games a year ago:
And here were the most successful rushing teams in the 2nd half:
If you look at how those numbers correlate to winning percentage, total 1st-half rushing yards have a Pearson coefficient of -0.090 (meaning there's practically no relationship -- and whatever relationship there is is negative!), while yards per rush in the 1st half have a 0.179 correlation with winning. 2nd-half total rushing yards have a correlation of 0.289 with winning percentage, and yards per carry in the 2nd half has a correlation of -0.303.
These are small correlations, but the point is that total 2nd-half rushing success is much more correlated with winning than 1st-half rushing (which has practically no relationship with winning whatsoever). In other words, so much for "establishing the run."
More interestingly, per-play rushing success in the 2nd half has the strongest correlation of any of the variables I looked at above... and it's negative! This makes sense, because teams running out the clock are often calling safe, straight-ahead plunge plays, while defenses with the lead are willing to concede effective runs to the trailing offense.
Because of those factors, the most telling numbers of all are simply that 1st-half rushing attempts had a -0.312 correlation with winning, while 2nd-half rushing attempts had a correlation of 0.612.
Which basically proves once again that teams need to establish the pass early, not the run, and use rushing to run out the clock once they have the lead.