In the middle of the 2017 season, I wrote a bit about completion percentage and first downs. Here’s one of my favorite charts to explain the evolution of the passing game in the NFL: the blue line shows completion percentage for each season in the NFL since 1960, a number that is steadily rising. The orange line shows first downs gained on completed passes in the NFL since 1960, which has been steadily declining:
How about first downs per pass play (including sacks)? That’s a number that’s been pretty consistent: it’s been between 28% and 33% every year, and while it’s showing a slight increase over time, it’s pretty slight.
What does this mean? One thing it means is that completion percentage is a less useful proxy for success than it used to be. The 2017 Ravens and Bucs (you know where this is going) serve as good examples. Baltimore completed 64.0% of passes last year, compared to 62.5% for Tampa Bay. But those completions didn’t do much for the Ravens: a league-low 46.3% of the team’s completions went for first downs, while a league-high 64.3% of completions in Tampa went for a first down. As a result, just 28.3% of Ravens pass plays [1]Note that this includes sacks, which I understand makes it a slightly apples-to-oranges comparison. But in this case, that helps the Ravens. Baltimore had a 4.5% sack rate, compared to 6.2% for … Continue reading went for a first down, compared to an NFL-best 37.7% for Tampa Bay.
The table below shows the completion percentage, first downs per completed pass, and first downs per pass play for each team in 2017.
| Team | Cmp | Att | Cmp% | 1D Pass | 1D/Cmp | Sk | 1D/PP |
|---|---|---|---|---|---|---|---|
| TAM | 378 | 605 | 62.5% | 243 | 64.3% | 40 | 37.7% |
| NWE | 389 | 587 | 66.3% | 232 | 59.6% | 35 | 37.3% |
| LAC | 366 | 583 | 62.8% | 220 | 60.1% | 18 | 36.6% |
| NOR | 386 | 536 | 72% | 201 | 52.1% | 20 | 36.2% |
| ATL | 343 | 530 | 64.7% | 200 | 58.3% | 24 | 36.1% |
| MIN | 357 | 527 | 67.7% | 196 | 54.9% | 27 | 35.4% |
| PIT | 384 | 590 | 65.1% | 217 | 56.5% | 24 | 35.3% |
| JAX | 316 | 527 | 60% | 193 | 61.1% | 24 | 35% |
| KAN | 363 | 543 | 66.9% | 198 | 54.5% | 37 | 34.1% |
| DET | 374 | 570 | 65.6% | 210 | 56.1% | 47 | 34% |
| LAR | 320 | 518 | 61.8% | 185 | 57.8% | 28 | 33.9% |
| WAS | 347 | 540 | 64.3% | 191 | 55% | 41 | 32.9% |
| PHI | 341 | 564 | 60.5% | 193 | 56.6% | 36 | 32.2% |
| SFO | 362 | 607 | 59.6% | 206 | 56.9% | 43 | 31.7% |
| CAR | 293 | 501 | 58.5% | 167 | 57% | 35 | 31.2% |
| HOU | 299 | 525 | 57% | 180 | 60.2% | 54 | 31.1% |
| DAL | 309 | 493 | 62.7% | 162 | 52.4% | 32 | 30.9% |
| ARI | 339 | 598 | 56.7% | 200 | 59% | 52 | 30.8% |
| SEA | 340 | 555 | 61.3% | 183 | 53.8% | 43 | 30.6% |
| OAK | 347 | 558 | 62.2% | 178 | 51.3% | 24 | 30.6% |
| CIN | 304 | 510 | 59.6% | 165 | 54.3% | 40 | 30% |
| TEN | 306 | 496 | 61.7% | 157 | 51.3% | 35 | 29.6% |
| MIA | 373 | 602 | 62% | 187 | 50.1% | 33 | 29.4% |
| DEN | 332 | 566 | 58.7% | 180 | 54.2% | 52 | 29.1% |
| GNB | 352 | 562 | 62.6% | 176 | 50% | 51 | 28.7% |
| BUF | 289 | 476 | 60.7% | 149 | 51.6% | 47 | 28.5% |
| BAL | 363 | 567 | 64% | 168 | 46.3% | 27 | 28.3% |
| NYJ | 323 | 510 | 63.3% | 157 | 48.6% | 47 | 28.2% |
| CHI | 291 | 473 | 61.5% | 144 | 49.5% | 39 | 28.1% |
| NYG | 373 | 608 | 61.3% | 178 | 47.7% | 34 | 27.7% |
| IND | 285 | 487 | 58.5% | 148 | 51.9% | 56 | 27.3% |
| CLE | 312 | 574 | 54.4% | 157 | 50.3% | 50 | 25.2% |
This stat does a nice job of finding the best passing offenses: the Bucs, Patriots, Chargers, Saints, Falcons, Vikings, and Steelers are the top ones by this metric, which forms a pretty good list considering it does not count touchdowns or interceptions… or even yards. Another interesting thing it does is highlight some offenses that might be underrated by traditional stats. The Jaguars, for example, ranked 2nd in the NFL in percentage of completed passes that went for a first down. That’s one reason the passing attack was better than people thought last year.
References
| ↑1 | Note that this includes sacks, which I understand makes it a slightly apples-to-oranges comparison. But in this case, that helps the Ravens. Baltimore had a 4.5% sack rate, compared to 6.2% for Tampa Bay. |
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