Midseason analytics review: Ohio State is clearly among the best teams, but where do they need work?

As Ohio State wraps up their bye week and preps for Northwestern, I thought it would be a good time to take a quick look at how Ohio State has performed so far this season.

Overall optimism around the program has grown nearly every week. But do the analytics match that enthusiasm?

One of the main metrics I will use to assess the Buckeyes is expected points added, or EPA. For anyone unfamiliar with EPA, here’s 538’s Josh Hermsmeyer’s definition: “EPA is calculated by taking the expected point value of every down, distance and field position (“game state”) combination before a play is run, and subtracting it from the expected point value of the new game state after a play is run.” The version of EPA we’re using here, thanks to Parker Fleming, also includes point differential and period.

Because EPA is calculated every play, we have the ability to not just say whether a play was successful or not (success rate) or explosive or not (explosiveness rate), but to also describe the magnitude of success or failure on any play, or for any player, or any offense/defense... etc.

Alright, let’s get to the stats.

Ohio State vs. other elite teams

• This chart plots offensive EPA on the x axis versus defensive EPA per play on the y axis.
• What is interesting here is that there are pretty clear tiers, or at least groups of teams. For example, if you draw a diagonal line to the left of Wisconsin, you can see a top tier of Wisconsin, Ohio State, Alabama, LSU, and Oklahoma. However, the Sooners and Tigers are clearly constructed a little differently — they’re the top two offensive EPA teams, but have a little lower defensive EPA than the other elite teams.
• Ohio State, as you can see, is midway between Alabama and Wisconsin in terms of offense/defense split. The game against the Badgers will be a heck of a matchup.

Justin Fields

• Justin Fields has had the unenviable task of following Dwayne Haskins, but he has really thrived. Even without the analytics, it’s easy to see Fields’ ability to throw across the field (on those numerous quick outs) and downfield accurately. He hasn’t been challenged to throw across the middle or on as many mesh routes as Haskins did last year, but it is clear that Day has tailored the offense to highlight Fields’ strengths.
• The chart above shows all FBS quarterbacks with 30+ drop backs, plotting EPA success rate (the ratio of positive to negative EPA plays) by average EPA. The trend line and confidence interval show what your expected average EPA would be based on your EPA success rate. If you think of EPA success rate as a measure of efficiency, then average EPA also incorporates explosiveness — and the magnitude of explosiveness — into the equation.
• Fields ranks 5th in the country in EPA success rate among QBs with 100 or more throws, but 21st in average EPA. As the chart above shows, Fields’ average EPA is a little under what you would expect given his extremely high success rate. As Tim Jessberger suggested on Twitter, this could be due in part to the fact that it seems like OSU receivers have fewer yards after catch this year compared to last. I don’t have depth of target or YAC data, but that seems like a good bet to me considering the Buckeyes have been relatively successful with deep passes.
• However, I do think that is at least something to watch — can Ohio State create more explosive pass plays either through yards after catch or through deep passes even with some elite defenses on the schedule?

Dobbins and the run game

• Like the QB chart, the top chart plots EPA success rate x average EPA for running backs with 40+ carries. From left to right, the OSU icons are Master Teague, J.K. Dobbins, and Fields near the top right of the chart.
• The next chart shows Dobbins’ average EPA by game in his career.
• One of the pleasant surprises this season has been that the run game has improved much more than I expected. Dobbins has recorded four games with over 140 rushing yards, while only getting two 140+ yard rushing games last season.
• It’s actually a little difficult to see Dobbins’ icon in the middle of the chart. That is a little interesting in the sense that we generally think of Dobbins as one of the top five or so running backs in the country, but EPA doesn’t exactly show that — at least yet.
• Fields is the visible OSU icon to the far right, with one of the highest EPA success rates as a rusher. That’s obviously impressive, and also indicative of the fact that quarterbacks generally have higher EPAs than RBs.
• Dobbins’ career EPA chart is really interesting. Basically his entire 2018 campaign had negative average EPAs per game, but all but FAU have been positive this season. However, his average EPA per game has declined week-to-week since his high against Cincinnati.
• On the season the team’s stuff rate is just 12.4%, which is really excellent — 4th in the country. However, it will be worth watching whether they keep that number low against Northwestern, Wisconsin, and Penn State.
• I thought the decline in average EPA could have been because of a slight increase in stuff rate game-to-game. But against Michigan State, the overall stuffed run rate was only 13%. However, their opportunity rate — the rate of 4+ yard runs — was the lowest against Michigan State at 45.6% (previously low was 53%). So that means that the Buckeyes were getting a lot of 1-3 yard runs against the Spartans.
• This is important because while the offense has been really elite, it also has essentially been able to stick to their efficiency-first script in almost every game. In other words, they haven’t yet been in a situation where they have needed to pass if the run game was getting consistently stuffed. That happened somewhat against the Spartans, but Michigan State didn’t have the offense to take advantage of their efficiency-limiting runs.
• So it will be critical for the Buckeyes to show they can pass, and pass explosively, if and when the run game gets slowed. That is my main concern for the Wisconsin and Penn State games.

Play calling

• This chart shows net EPA, which is average pass EPA - rush EPA, by standard down rush rate. Essentially, this shows whether teams are better passing than rushing (the x axis, with the right side of the chart being better passing) by how often you run on standard downs when you have the option of either rushing or passing. It creates four quadrants based on your offensive strength and whether you tend to rush or pass.
• Ohio State is in the quadrant of teams that are more effective passing than rushing, but they tend to rush on standard downs. This could suggest that the Buckeyes could vary it up a little on early downs, but it is also worth noting that the Buckeyes are very close to no difference between their average rushing and passing EPAs. Essentially, they’re a very balanced team in terms of their effectiveness through the air vs. on the ground.

Defense notes

• The defense’s improvement has really been the story of the season to me. Ohio State is third in the country among FBS teams in average EPA and 4th in EPA success rate.
• They are 2nd overall in passing EPA, although this is a good time to note that they haven’t really faced a strong passing offense yet.
• They’re really strong in the red zone, ranking 5th in opponent red zone success rate, 3rd in even allowing opponents to get scoring opportunities in the first place, 3rd in touchdown rate once an opponent has gotten within the 40, and 10th in overall havoc rate (thanks, Chase Young!).
• One thing to note is that they are much better on passing downs than standard downs, ranking 30th in standard downs success rate vs. 15th in passing downs success rate. That split is more apparent in EPA, as they have an average standard downs EPA of 0.04 (positive is not good), but -0.36 in passing downs EPA (which is 1.2 standard deviations from the mean, 6th overall).