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Predicting Ohio State's 2014: Unknown defense

This is the second part in our advanced statistical preview of the 2014 season. See the first part on the offense here.

Gregory Shamus

Last week we took a look at what the advanced statistics from Football Outsiders and Football Study Hall have to say about the 2014 Buckeye offense. Now it's the defense's turn.

Despite returning seven players from last season's squad, I'm sure a large percentage of the fanbase would be alright if eleven Joey Bosa clones jogged onto the field against Navy.

That's because the 2013 defense was just okay. As in, okay enough to make the Big Ten Championship, but not okay enough to fulfill the national championship-level preseason dreams.

Even though there are more returning starters on defense than on offense, arguably more variables have changed for the defense such that it's difficult to project exactly how the 2014 defense will perform as a unit.The 2013 Defensive F/+ was 3.9%, which put the Silver Bullets 45th overall. Both the FEI (the drive-based measure) and S&P+ (the play-based measure) ranked them as 42nd overall. While you would hope that the play-by-play and drive-based measures of defensive efficiency and defensive explosiveness are correlated, they're the exact same in their evaluations of the Buckeyes. That's good for the validity of the variables and not so good for the Buckeyes.

Most analyses of last season's defense noted the poor secondary play that turned opposing quarterbacks into Peyton Manning, the unaggressive zone scheme, the absent linebacker play, and the inconsistent (if at times dominant) defensive line. But, to most, it was really that pass defense that did the Buckeyes in.

However, after reviewing the numbers, that analysis seems to be only half true.

2013: Mediocrity all around

Before the Big Ten Championship, Connor Cook was Just Another Big Ten Quarterback. Then he gets in front of the Buckeye defense and throws for 304 yards, his highest total of the season. The previous week, Minnesota held Cook to 143 yards and an interception. Minnesota.

So, that shouldn't happen when you've got national championship aspirations. Neither should anyone every throw for 451 yards against your defense, but that's exactly what happened in The Game as Devin Gardner attempted 45 passes. Ultimately, opposing offensive coordinators learned that they could just throw the ball over and over again and eventually the Buckeye defense would give up points.

However, what's maybe most interesting about that narrative is that it's not entirely true: the opponent-adjusted play-by-play metrics suggest that the rushing defense was just as mediocre as the passing defense.

Only the S&P+ separates rushing and passing plays, so that's what we'll look at here. Defensive S&P+ is partly based on the ability of a defense to prevent an offense from creating "successful" plays. Successful plays for the offense are ones that gain 50% of the necessary yardage on first down (i.e., ten yards on a normal first down), 70% on second down, and 100% on third down. This is the efficiency half of S&P+.

The other part of S&P+ factors in the fact that all yards aren't created equal -- which according to Bill Conelly, means that "This assigns credit to the yards that are most associated with scoring points." So after assigning a point value for each play in a drive based on starting and ending field position, you can measure points or play, or explosiveness. Combining those two -- and then adjusting based on the opponent -- gives you a team's S&P+. The best defenses limit both efficiency and explosiveness. Opposing offenses don't have much success either methodically driving the ball or hitting big plays.

S&P+ scores are set to an average of 100, where over 100 means above-average. The Buckeyes had a Defensive Rushing S&P+ of 103.4 and a Defensive Passing S&P+ of 101.2, ranked 58th and 61st, respectively. It doesn't get much more average than that.

What's amazing is how average both scores are. Based on the narrative above, and how the defenses ended up collapsing in both losses (and the near-loss to Michigan), you might expect the Passing S&P+ to be really bad, but the rushing defense to be significantly above-average. After all, the Silver Bullets didn't allow a 100-yard rusher until Jeremy Langford in the Big Ten Championship.

However, while the Defensive Rushing and Passing S&P+ scores were nearly identical, the Standard and Passing Downs S&P+ scores actually varied quite a bit. The Standard Downs S&P+ was 97.7 (79th overall) and the Passing Downs S&P+ was 108.2 (42nd). That's a fairly interesting mix of rankings: equally mediocre against the run and the pass, but much better on passing downs than standard downs.

Does that mean that opposing offenses were relatively more successful passing on standard downs than they were passing on passing downs? That's my initial thought, as the defense was pretty good at preventing long bombs, but could be dinked-and-dunked all the way down the field -- and I could see opposing offensive coordinators turning to short passes and screen more on standard downs anyway. We'd need more charting data here to really parse that out definitively, but that's my hunch based on the numbers and the way the defense played.

Bend but don't break quantified

While there was relative balance between the defense's ability to stop the run and the pass last season, the defense was actually much better at stopping explosive plays than in being efficient (relative to the rest of college football).

For instance, the Defensive Success Rate+ was 97.5, or 66th overall, but the Defensive IsoPPP+ was 104.2, or 42nd overall. Again, looking at the numbers altogether, it looks like opposing offenses just used screens and short passes methodically down the field, rather than picking up large chunks of yards at once. 42nd in limiting explosive plays is nothing to brag about, but hey, it's better than average.

Worst when it mattered most

Unfortunately, the defense did not tighten up in the red zone. The Buckeyes had a Defensive Red Zone S&P+ of 87.9, or 93rd in the country, which puts them among the worst in the country. To balance that out, at least the offense was the best in the country in Offensive Red Zone S&P+!

★★★

If I've sounded harsh on last year's defense, there's still (a lot of) hope for 2014. Tyvis Powell and Vonn Bell (not to mention Cam Burrows and Erick Smith) are now at safety, and there are at least four starter-quality corners ready to anchor the secondary. The defensive line is full of incredible athletes who just need to stay healthy, out of trouble, and in opposing backfields consistently. The linebacking corps has a renewed stockpile of (mostly unproven) talent.

But the real change might just be schematic. The addition to Chris Ash as co-defensive coordinator has the potential to drastically affect the team's aggressiveness and the playing speed for the defense. Coaching changes aren't factored in to 2014 projected rankings, but Football Outsiders projects that the 2014 Silver Bullets will have the 31st-ranked defense just from the numbers alone.

And you know what? I'll take that gladly.