What were the major trends in Ohio State's regular season?

With the Buckeyes likely headed to a New Year's Day Bowl against either Stanford or Notre Dame, it's as good a place as any to look at how Ohio State's season played out by the numbers.

Season-long trends

Adjusted scoring margin takes your single-game offensive S&P+ performance and converts it in to points, effectively creating a new game score based on how the advanced stats suggest the game went.

Effectively, a season's worth of adjusted scoring margins shows how variable the Buckeyes were week-to-week this year. With low adjusted scoring margins against Northern Illinois, Western Michigan, Indiana, Maryland, and Minnesota (not to mention Michigan State), this chart captures how the media viewed Ohio State's regular season: good, but underachieving relative to the talent in place.

Comparing percentile performance and Ohio State's opponents' S&P+ rankings gives a similar feeling from the adjusted scoring margins chart: Ohio State should have beaten a few overmatched teams by a lot more than they actually did. For instance, Ohio State played one of its worst games of the season against the third-worst team on its schedule in Maryland, which ranks 74th in the S&P+ rankings (Ohio State had an 84% performance against the Terrapins).

This year Ohio State averaged an 87% percentile performance, but had five games sub-90%, including a 55% against the Spartans. Last season, following a 49% performance in the loss to Virginia Tech, Ohio State had just two games sub-90% -- an 81% performance against Indiana and 74% in the win over Alabama. They averaged a 90% performance overall last year.

The Buckeyes had the highest percentage of games in the 90th percentile last year (73%), best in the country, while this year just 58% of their games were in the 90th percentile. Ohio State was able to jump in to the playoff last season because they were dominant following their early-season win. Last year Ohio State had four games in the 99th or 100th percentile (Kent State, Rutgers, Illinois, and Wisconsin), but Ohio State's best game this season were two 97% performances against Illinois and Michigan. This year, Ohio State was far from dominant, with a lower average performance and a lower floor.

The biggest improvements

Ohio State's defense was a pleasant surprise this season. Not much changed personnel-wise -- Tyquan Lewis, Gareon Conley, and Raekwon McMillian became starters -- but the defense improved from eleventh to eighth in defensive S&P+. That's not a huge jump, but the Buckeyes were vastly improved in two areas: red zone defense and in run defense.

First, Ohio State allowed 4.6 points per opponent trip inside their forty yard line last season (88th in the country). This year, the Buckeyes allowed just 3.7 points (9th) -- nearly a whole point per scoring opportunity less! Second, one of the biggest concerns coming in to the season was how the Buckeyes would perform against great running teams. Yes, the Buckeyes shut down Melvin Gordon in the 2014 Big Ten Championship, but they ranked 42nd in defensive rushing S&P+ and 45th in rushing success rate last season. This year, Ohio State jumped to 18th in defensive S&P+ and fifth in defensive rushing opportunity rate. Indiana, Northern Illinois, and Western Michigan had varying success with big running plays, but overall the defense improved markedly on the ground and in the red zone.

The Buckeyes regressed in turnover margin

Ohio State was 27th in the country in turnover margin at +7 on the year last season. This was through takeaways, as the Buckeyes were fifth overall with 33 takeaways (and 101st in total lost last season). This year, the Buckeyes are 52nd at just +2 in turnover margin, with just 19 takeaways (67th). Turnovers are somewhat based on luck and somewhat based on skill (some interceptions are randomly tipped passes, some are terrible decisions to throw in to coverage), so a big swing in turnover margin can drastically affect the whole season.

As a side note, turnovers don't explain the loss to Michigan State, as the Buckeyes were +2 in that one.