Silent Archimedes

Point differential a telling statistic in the NFL

Posted by silentarchimedes on December 16, 2008

On November 3, I wrote a blog comment on ESPN‘s Matt Mosley’s NFC East blog article Rapid Reaction: Steelers 23 Redskins 6 :

“What this game has shown is that the Redskins have actually been very lucky with their six wins. Simply look at the point differential. They have scored 171 points but have given up 168! That 3 point differential usually means a .500 record. The Eagles even have a +76 pt diff. The division leading Giants have a +97. The Cowboys have a -3. Seems like the Redskins are closer to the Cowboys. I’d have to say the Eagles are 2nd best in East now. Both Eagles and Giants beat the Steelers, while Skins got destroyed.”

The Redskins were 6-2 before losing to the Steelers. Redskins fans attempted to deride my analysis as simply a Giants fan hating on the resurgent Skins. One fan even said “I think you’re crazy man.” However, ever since my comments, the Redskins proceeded to lose four of their next five games and now sit in last place in the NFC East with a 7-7 record. Their point differential is now a horrible -35. Let’s look quickly at the rest of the NFC East:

NFC EAST W L T PCT PF PA PT DIFF since Nov 3
z- NY Giants 11 3 0 .786 374 246 +128 +31
Dallas 9 5 0 .643 332 288 +44 +47
Philadelphia 8 5 1 .607 369 273 +96 +20
Washington 7 7 0 .500 231 266 -35 -32

Point differential is a very telling statistic of how good a football team is. Although the saying “A win is a win is a win” is true, how well you win or how bad you lose a game provide clues into the momentum of a team. Point differential captures the spread between the strength of the offense’s ability to score points and the defense’s ability to limit points. It also captures the ability of the special teams to do both as well. When a good team consistently maximizes this ratio, the point differential steadily increases and builds over the course of the season.

How telling is the statistic? In 6 of the 8 divisions in the NFL, the division leader has the best point differential. The AFC North, where the Ravens (+112) have a tiny edge on the division leading Steelers (+110) is basically a tie. The only division where this is  not true is the AFC West, where the Broncos -40 leads the Chargers +44. In 7 of 8 divisions, the cellar team has the worst point differential. Once again, in the AFC West, the Raiders -143 is worse than the cellar Chiefs at -132. It is the teams in the middle, where their inconsistency in winning give true meaning to “Any Given Sunday.” Division leaders and bottom feeders do not strongly abide by that saying because they consistently win or lose.

I am surprised that ESPN does not have point differential as a column statistic. The NFL website does. Since point differential is a derived statistic, (Points for – Points Against), ESPN’s thinking is that there does not need to be a column for it.

Patriots flying high

Patriots flying high

So, what team had the greatest point differential in a season since the16-game season was instituted in 1978? Yup, you guessed it. The 2007 16-0 New England Patriots, whose +315 was 127 more than that year’s second place Indianapolis Colts’ (+188) and 413 more than the AFC East’s second place Buffalo Bills (-102). The next team with the best point differential since 1978 were the 1999 St. Louis Rams, whose +284 led to a 13-3 record and a Super Bowl. Which team had the worst -274 point differential since 1978? The 1981 2-14 Baltimore Colts. The 1990 1-15 Patriots had the second worst point differential with -265.

Point differential is now used extensively in the NBA because of how telling it is. The amount of games in a season and points in a game in the NBA coupled with the consistency of the players and plays provides a more predictable environment. However, good teams and bad teams in the NFL also prove year in and year out that point differential is also a good indicator of the strength of a team.

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