How should you divide credit between the offensive line and running backs on rush plays? One method is Line Yards, a metric developed by Football Outsiders to capture the contribution of the line.
Based on regression analysis, the Line Yardage formula takes all running back carries and assigns responsibility to the offensive line based on the following percentages:
- Losses: 120% value
- 0-4 Yards: 100% value
- 5-10 Yards: 50% value
- 11+ yards: 0% value
The offensive line gets full credit for the first 4 yards of any run, but half credit for the next 6 as the running back gets past the defensive line. The running back gets full credit beyond 10 yards.
To give a football example of how this works, consider the line yards per carry for Michigan through week 10 for the 2017 season.
- Florida: 2.86
- Cincinnati: 2.55
- Air Force: 2.68
- at Purdue: 2.41
- Michigan State: 3.19
- at Indiana: 3.23
- at Penn State: 3.48
- Rutgers: 3.62
- Minnesota: 3.54
Michigan struggled early in the season against teams like Air Force and Purdue. But since the Michigan State game, Michigan’s run blocking has improved by line yards per carry.
The last two games show how line yards breaks down the contribution between the offensive line and running backs.
Against Rutgers, Michigan had 3.62 line yards per carry. They rushed for 334 yards on 6.55 yards per carry (numbers do not include sacks, although Michigan didn’t allow any against Rutgers).
Michigan had slightly worse line yards per carry against Minnesota: 3.54 compared to the 3.62 against Rutgers. However, the offense rushed for 394 yards on 11.59 yards per carry, an astounding rate.
The line yards gives about the same credit to the Michigan’s offensive line against both Rutgers and Minnesota.
The running backs get the extra credit against Minnesota, as Karan Higdon (47, 77 yards) and Chris Evans (60, 67 yards) both broke long runs. In contrast, Michigan’s longest runs were 49 and 32 against Rutgers.
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