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When I watch teams other than those that throw the ball on most plays, it feels like coaches always run the ball after first down incompletions. It's like they think they took a risk that didn't pay off on first down, and now they just want to get something, anything before third down.
I used the NCAA's play-by-play data for the season's first month to try to answer this question. I found all first down incompletions that had some kind of standard play afterwards (not field goals or the end of games or anything). I tossed out all interceptions, of course. I also eliminated incompletions that were followed by penalties, because penalties change the calculus. I just wanted to see what happened after first down incompletions.
For all FBS offenses, they run 52.8% of the time after first down incompletions. The idea that teams always run after first down incompletions isn't even close to true.
Not ready to give up, I narrowed it down to just SEC teams, because those are the teams I watch most. I also decided to cross-check the run rates on second down following an incompletion against Bill Connelly's data on how often the teams run on passing downs. Passing downs are 2nd-and-8 or longer, 3rd-and-5 or longer, and 4th-and-5 or longer.
What I saw was one of my favorite findings I've ever had with stats.
| Team | 1st Down Inc.'s | Next Play Run Pct. | Pass Downs Run Rate | Difference |
|---|---|---|---|---|
| LSU | 5 | 100.0% | 57.1% | +42.9% |
| Arkansas | 10 | 60.0% | 22.4% | +37.6% |
| Florida | 21 | 71.4% | 36.9% | +34.5% |
| Texas A&M | 21 | 76.2% | 42.4% | +33.8% |
| Tennessee | 13 | 76.9% | 45.7% | +31.2% |
| Auburn | 4 | 50.0% | 22.1% | +27.9% |
| Vanderbilt | 20 | 70.0% | 45.4% | +24.6% |
| Kentucky | 11 | 63.6% | 39.2% | +24.4% |
| Mississippi State | 23 | 52.2% | 30.1% | +22.1% |
| Alabama | 25 | 32.0% | 23.6% | +8.4% |
| Missouri | 20 | 40.0% | 33.3% | +6.7% |
| Georgia | 4 | 25.0% | 25.0% | 0.0% |
| South Carolina | 12 | 33.3% | 34.7% | -1.4% |
| Ole Miss | 21 | 19.0% | 23.1% | -4.1% |
In general, SEC teams are much more likely to run after a first down incompletion than they are in other passing downs. Nine of the 14 teams have run rates after first down incompletions that are at least 20 percentage points higher than on all passing downs. Pass-happy Ole Miss and passing enthusiast Steve Spurrier buck the trend. Georgia is right on, although Greyson Lambert hasn't been throwing many incompletions to really set a pattern. Everyone else is conforms to the trend.
Obviously, there's room to slice and dice this data by situation, like scoring margin and how late in the game it is. For example, three of Florida's six passes after first down incompletions came while down 13 points to Tennessee. Jim McElwain's preference might be more run heavy than these figures imply, but the realities of staging a late game comeback could've forced him to throw more than he'd naturally like to. That kind of analysis is something for the end of the season when the data set is much larger.
Anyway, maybe teams don't always run after first down incompletions. But inside the SEC at least, most teams are more likely to run after a first down incompletion than in other passing situations. The feeling is justified.