Completion percentages continue to skyrocket, and part of the reason for the increase is the rise of low value completions. As a result, the best way to measure the consistency of a passing game isn’t with completion percentage, but with passing first down percentage. That’s defined as simply:
Passing First Downs / (Pass Attempts + Sacks)
As noted last week, the Giants and Texans provided good real world examples for 2018. Through four weeks, Houston ranked 25th in completion percentage but 8th in passing first down percentage. Meanwhile, the Giants ranked 2nd in completion percentage but 22nd in passing first down percentage. My proposition is that passing first down percentage is a better reflection of the passing game and a more meaningful statistic than completion percentage; and that’s why, through four weeks, Houston ranked 15th in points/game, while the Giants ranked 29th.
But does that argument hold up over time? How do we *know* that Passing 1st Down Rate is more important than Completion Percentage? Here’s a simply study I did.
1) Calculate the completion percentage relative to league average for every team since 1970.
2) Calculate the passing first down percentage relative to league average for every team since 1970.
3) Identify teams that ranked two percentage points better than league average in one metric and two percentage points worse than league average in the other metric.
4) Compare those teams.
High Completion Percentage, Low Passing First Down Rate
There have been 22 teams that finished two percentage points above league average in completion percentage and two percentage points below league average in passing first down rate. Those 22 are presented below. Here’s how to read the table below. In 2015, Kansas City completed 65.5% of passes, which ranked 9th in the NFL, and was 2.5% above league average. The Chiefs gained a first down, however, on just 29.9% of all passing plays, which ranked 26th in the NFL and was 2.4% below average. Kansas City ranked 9th in points and was 2.5 points per game better than average, while posting a 0.688 winning percentage.
| Team | Year | Cmp% | Cmp% Rk | Cmp% Ov Avg | 1D/PP | 1D/PP Rk% | 1D Ov Avg% | Pts Rk | PPG vs. Avg | Win% |
|---|---|---|---|---|---|---|---|---|---|---|
| KAN | 2015 | 65.5% | 9 | 2.5% | 29.9% | 26 | -2.4% | 9 | 2.5 | 0.688 |
| PHI | 2015 | 65% | 10 | 2% | 29.2% | 28 | -3% | 13 | 0.8 | 0.438 |
| WAS | 2014 | 66.5% | 4 | 3.9% | 30.7% | 23 | -2.2% | 26 | -3.8 | 0.25 |
| CHI | 2014 | 65% | 10 | 2.4% | 29.8% | 27 | -3.1% | 23 | -2.7 | 0.313 |
| BUF | 2006 | 62.2% | 9 | 2.4% | 27.6% | 27 | -3.5% | 23 | -1.9 | 0.438 |
| CLE | 2006 | 62.1% | 10 | 2.3% | 27% | 30 | -4% | 30 | -5.8 | 0.25 |
| CLE | 2003 | 61.5% | 10 | 2.7% | 27.9% | 21 | -2.3% | 29 | -5 | 0.313 |
| TAM | 1999 | 60% | 5 | 2.9% | 27% | 24 | -2.7% | 27 | -3.9 | 0.688 |
| CIN | 1998 | 58.9% | 7 | 2.3% | 25.8% | 26 | -4.3% | 27 | -4.5 | 0.188 |
| IND | 1991 | 59.6% | 7 | 2.2% | 28.6% | 22 | -2.5% | 28 | -10 | 0.063 |
| CLE | 1989 | 58.4% | 9 | 2.6% | 28.6% | 20 | -2.3% | 14 | 0.3 | 0.594 |
| BUF | 1986 | 58.9% | 6 | 3.5% | 27.9% | 19 | -2.4% | 20 | -2.6 | 0.25 |
| ATL | 1984 | 61.5% | 4 | 5.1% | 27.7% | 21 | -3% | 22 | -3.6 | 0.25 |
| NYJ | 1983 | 59% | 8 | 2.1% | 28.4% | 19 | -2.2% | 19 | -2.3 | 0.438 |
| HOU | 1981 | 58.5% | 6 | 3.9% | 25.8% | 24 | -4.3% | 23 | -3.1 | 0.438 |
| WAS | 1980 | 58.4% | 9 | 2.3% | 28.4% | 20 | -2.4% | 25 | -4.2 | 0.375 |
| SFO | 1980 | 60.8% | 3 | 4.6% | 27.3% | 24 | -3.5% | 12 | -0.5 | 0.375 |
| KAN | 1980 | 59.1% | 4 | 2.9% | 26.6% | 26 | -4.1% | 14 | -0.5 | 0.5 |
| BAL | 1979 | 56.9% | 7 | 2.8% | 26.2% | 22 | -3.3% | 22 | -3.1 | 0.313 |
| KAN | 1978 | 55.1% | 11 | 2.1% | 25.1% | 25 | -3.9% | 24 | -3.1 | 0.25 |
| HOU | 1974 | 55.9% | 8 | 3.5% | 26% | 19 | -2.3% | 17 | -1.3 | 0.5 |
| HOU | 1973 | 54.7% | 8 | 2.7% | 20.5% | 26 | -7.4% | 23 | -5.2 | 0.071 |
| Avg | 60.2% | 7.5 | 2.9% | 27.4% | 23.6 | -3.2% | 21.4 | -2.9 | 0.363 |
As it turns out, the 2015 Chiefs are an outlier: The average team was about 3% above average in completion percentage, 3% below average in 1st Down rate, but finished 2.9 points per game below average and posted a 0.363 winning percentage (slightly worse than a 6-10 season). This means these above-average passing attacks — as measured by completion percentage — weren’t translating to points and wins.
Low Completion Percentage, High Passing First Down Rate
There were also 22 teams that finished two percentage points below average in completion percentage and two percentage points above average in passing first down rate. This was most recently done by the 2017 Jaguars, who had a 60% completion rate, which ranked 24th and was 2.1% below average, and had a 35% Passing 1D Rate, which was 8th and 3.3% above average. Jacksonville finished 5th in scoring, at 4.3 points above average, and had a 0.625 winning percentage.
| Team | Year | Cmp% | Cmp% Rk | Cmp% Ov Avg | 1D/PP | 1D/PP Rk% | 1D Ov Avg% | Pts Rk | PPG vs. Avg | Win% |
|---|---|---|---|---|---|---|---|---|---|---|
| JAX | 2017 | 60% | 24 | -2.1% | 35% | 8 | 3.3% | 5 | 4.3 | 0.625 |
| CAR | 2015 | 59.9% | 27 | -3.1% | 36.9% | 2 | 4.6% | 1 | 8.4 | 0.938 |
| TAM | 2015 | 58.3% | 29 | -4.7% | 35.8% | 3 | 3.5% | 20 | -1.4 | 0.375 |
| CLE | 2007 | 56% | 30 | -5.2% | 34% | 14 | 2% | 8 | 3.4 | 0.625 |
| ATL | 1999 | 54.6% | 27 | -2.5% | 32.1% | 8 | 2.4% | 23 | -3 | 0.313 |
| SEA | 1999 | 54.9% | 25 | -2.2% | 31.8% | 10 | 2.1% | 12 | 0.3 | 0.563 |
| WAS | 1997 | 51.7% | 27 | -4.5% | 33.1% | 5 | 3.2% | 15 | -0.3 | 0.531 |
| ARI | 1996 | 54.8% | 23 | -2.8% | 33% | 6 | 2.3% | 22 | -1.7 | 0.438 |
| DET | 1994 | 54.5% | 22 | -3.6% | 33.8% | 5 | 2.9% | 6 | 2.1 | 0.563 |
| HOU | 1988 | 50.9% | 24 | -3.3% | 32.7% | 8 | 2.3% | 2 | 6.2 | 0.625 |
| PIT | 1984 | 54.2% | 19 | -2.2% | 34.9% | 3 | 4.2% | 8 | 3 | 0.563 |
| NYG | 1984 | 53.8% | 21 | -2.5% | 33.6% | 6 | 2.8% | 19 | -2.5 | 0.563 |
| TAM | 1982 | 53.2% | 23 | -3.2% | 32.9% | 4 | 2.6% | 18 | -2.6 | 0.556 |
| GNB | 1982 | 53.6% | 21 | -2.8% | 32.4% | 7 | 2.1% | 5 | 5 | 0.611 |
| TAM | 1981 | 50.5% | 23 | -4.1% | 32.3% | 6 | 2.2% | 18 | -1 | 0.563 |
| PIT | 1980 | 51.7% | 24 | -4.5% | 34% | 6 | 3.2% | 10 | 1.5 | 0.563 |
| PHI | 1979 | 51% | 22 | -3.1% | 33.8% | 4 | 4.2% | 12 | 1.1 | 0.688 |
| SDG | 1974 | 47.3% | 22 | -5.2% | 31.5% | 7 | 3.2% | 20 | -3 | 0.357 |
| RAM | 1974 | 50% | 17 | -2.5% | 31.2% | 8 | 2.9% | 13 | 0.6 | 0.714 |
| NYJ | 1972 | 49.6% | 18 | -2.1% | 32.1% | 4 | 3.3% | 2 | 6 | 0.5 |
| GNB | 1971 | 47.6% | 20 | -3.2% | 32% | 4 | 3.9% | 13 | 0.2 | 0.357 |
| CLE | 1970 | 48.5% | 22 | -2.7% | 32.8% | 3 | 5% | 13 | 1.2 | 0.5 |
| Avg | 53% | 23.2 | -3.3% | 33.3% | 6.0 | 3.1% | 12.0 | 1.3 | 0.551 |
On average, these 22 teams were over 3 points below average in completion percentage but over 3 percentage points above average in Passing 1st Down Rate. These teams finished 1.3 points per game above average and won 55.1% of their games. The 1988 Oilers and 2015 Panthers are great examples of teams that had poor completion percentages but big play passing games that translates into points and wins.
While not conclusive, of course, this evidence supports what I think is also a pretty easy to believe proposition in the first place: that passing 1st down rate is more important than completion percentage.