Advanced stats to watch for Justin Fields, J.K. Dobbins against FAU

Ohio State shouldn’t have any (or at least much) trouble with FAU. Vegas odds (via Bovada) have the Buckeyes favored by 28.5, and SP+ favors the Buckeyes by 26.5 with a 94 percent win probability.

But we can still learn some things about the 2019 Buckeyes by taking a look at some advanced stats after the game. So here are the main things that I’ll be paying attention to.

---

Justin Fields’ passing efficiency

This is an obvious one — how will the new quarterback do? In many ways, I think Ohio State’s ceiling will be somewhat determined by the level of efficiency that the passing game can maintain this year. Last season’s passing offense ranked fifth in passing SP+ and third in passing marginal efficiency.

Dwayne Haskins also ranked third in EPA success rate and seventh in average EPA last season. EPA stands for “expected points added” and is calculated by estimating the expected points for every down, distance, and field position combination possible (i.e. second and three on your opponent’s 45 yard line). A play’s actual result (i.e. a four-yard gain) is then compared with those expected points to give you EPA. (Read more about EPA here over at Frogs O War.)

The tl;dr is that it quantitatively rates the magnitude of success or failure for every single play. And we can do a lot of awesome stuff with that information — looking at average EPA per player and play types, or the volatility of EPA by opponent, etc. As far as I’m aware, historical EPA data is pretty new to college football, although the nflscrapR team has provided it for a while at the NFL level — so thank you, @903124! Hopefully we’ll have week--by-week EPA data moving forward thanks to collegefootballdata.com and Parker Fleming.

Two stats you can look at are average EPA on a given play — which gives you a sense for how good an average play is — and EPA success rate — which is basically the percentage of positive EPA plays.

Here’s Haskins (the bigger, red dot) from last season, relative to every other quarterback with at least 75 passing attempts:

The red line at zero is the cutoff between a positive and a negative play. The dotted lines are the FBS averages in quarterback average EPA and EPA success rate.

So it should be obvious that Haskins was really in an elite group of five players with a success rate over 55 percent. Just seven players had a mean EPA over .45.

That’s a very high bar for Fields to live up to. So when you’re watching Fields on Saturday, albeit against a pretty poor defense (projected at 89th in defensive SP+), it’s really worth watching how efficient the passing game is — both overall and situationally. Ohio State’s offense was fifth overall in passing downs SP+ last season, ranking 17th and 12th in third-and-long and third-and-medium success rates. Being able to consistently move the chains, and in particular, in must-throw situations, will be key against tougher defenses later in the year.

---

Dobbins avoiding negative plays, hitting more explosive plays

The passing game exploded last year, but the run game was fairly mediocre for the first time in seemingly forever:

The above chart, courtesy of collegefootballdata.com, shows both the incredible increase in rushing SP+ when Urban Meyer was hired to be Ohio State’s 24th head coach, as well as the insane drop last year to below the Big Ten average. The run game fell to 54th in rushing SP+ and 41st in marginal efficiency, as 18.8 percent (66th!) of runs got stuffed at or behind the line of scrimmage. Oof.

There were multiple problems — at running back, on the offensive line, and the playcalling itself. But with a new season (and time during the offseason to work out the kinks) it’s possible that the rushing offense rebounds in 2019. So that’s what I’ll be watching for — J.K. Dobbins’ overall efficiency.

Dobbins averaged 4.6 yards per carry last season, gaining four or more yards on 53.5 percent of carries. Here’s the same chart for Dobbins as we did for Fields — EPA success rate vs. average EPA:

This chart includes both quarterbacks and running backs, and is limited to rushers with at least 50 carries.

The chart shows that Dobbins was above-average in efficiency (but still not mind-blowing levels, he ranked ~100th in EPA success rate) and below-average in average EPA. That combination indicates that he had a significant number of negative plays (and not many explosive runs) to bring down his average EPA, since 49.8 percent of his runs had a positive EPA. Dobbins was approximately 279th in average rushing EPA last year.

I’d easily bet that those numbers are a strong decline from his freshman season, although I haven’t pulled the actual EPA numbers yet.

Dobbins was 37th in the country in the most stuffed runs, with 32. Additionally, if you look at the number of 13+ yard runs by rushers last season, Dobbins was tied for ~120th with 13 runs. He only had four runs of 20+ yards last season, too.

For context, Wisconsin’s Jonathan Taylor was second in the country with 35 runs of 13+ yards. So Dobbins had about 41 percent as many explosive runs as he did runs stuffed last year. Obviously a lot of that is on the offensive line, but either way, the Ohio State run game must improve this year.

This chart visualizes the split between rusher stuffed runs and explosive runs of 13+ yards, with Dobbins in red:

So I’ll be watching for rushing efficiency from Dobbins, but I’ll also be looking for whether he and the other running backs can avoid negative plays while generating a few 13+ yard runs, too.

Specifically, we should be happy with between a 12.2 percent to ~14 percent (what Ohio State averaged in 2017 and 2016) stuff rate, while generating a few more explosive runs per game.