The people over at Pro Football Focus have once again compiled a trove of interesting information, this time on rushing statistics. But information is just information, of course; it’s how you interpret it that brings value.
PFF compiled data on the 73,000 or so carries over the last five seasons around the NFL by a tailback in the backfield and created a chart demonstrating a positive correlation between the number of defensive backs on the field for the defense and the amount of yards per carry the offense was able to average.
The hypothesis is obvious enough: the more big bodies there are to run against, the more difficult it is to run the ball. But seeing the data compiled and organized all in one place gives an interesting and concrete perspective on the idea.
Of the approximately 73,000 carries that they charted, 48,307 of them, or about two thirds, came against base defenses with four defensive backs on the field, and in those situations, backs averaged 4.2 yards per carry.
Unsurprisingly, the second-most frequently run against defense is the nickel with five defensive backs on the field, which saw 18,498 rushing attempts to defend, or about 25 percent of the total logged carries. Backs had greater success carrying the ball by nearly half a yard, averaging 4.6 yards per carry.
That number begins to spike rapidly against the dime defense with six defensive backs on the field, as backs averaged 5.6 yards per carry against that personnel. It needs to be noted that the sample size is substantially smaller, however, at 2815 total plays, which is only about four percent of the total sample size.
There were just 92 total carries logged with seven defensive backs on the field, but against such defenses, running backs were able to average 7.3 yards per carry. Removing defensive backs has the opposite effect.
With three defensive backs on the field, running backs averaged just 2.3 yards on 2449 carries. With one or two defensive backs, they averaged 0.7 and 0.9 yards, respectively. Of course, these runs generally come at the goal line or in short-yardage situations.
Based on last season, the numbers are skewing toward more runs against sub-packages, however. According to PFF, only 61 percent of carries came against base defenses or with less than four defensive backs on the field, with about five percent of carries coming against six or more defensive backs.
The Pittsburgh Steelers saw some of the least resistance with big bodies, ranking 25th in the league in terms of the percentage of their carries coming against four or less defensive backs. About 47 percent of their carries came against sub-packages. The Broncos, meanwhile, only faced five or more defensive backs 22 percent of the time.
The 49ers had the opposite, facing base defense or extra big bodies an astounding 92 percent of the time. 14 percent of their carries came against three or less defensive backs, yet they still averaged 4.4 yards per carry on the year, nearly a yard better than the Steelers, who ranked third from the bottom in yards per carry, despite facing more defensive backs than most teams.