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Nebraska Football

Hot Reads: Is a 125% Decrease Bad? It Has Been for the Huskers Offense

October 17, 2019
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Let's talk about Nebraska's first six plays of the season.

The Huskers won the toss in the opener against South Alabama and Scott Frost opted to take the ball, as he usually does. This was perfect. Let's get that Year 2 offense on the field and see what it can do against a five-touchdown underdog. Surely, there will be blood.

And there was, eventually, but the first two series of the eventual touchdown drive were pretty shaky. Let's look at those plays quickly from a Predicted Points Added (PPA) perspective. (Numbers courtesy of collegefootballdata.com

It's a pretty simple concept. Every yard line has a predicted point value (based on historical modeling) and that value changes based on down and distance. Every play run then can be given a point value based on how it increases or decreases a team's predicted points and this is PPA. ESPN uses a similar set up for QBR.

Here are Nebraska's first six plays of the first drive of the season with PPA so you can see it at work.

Down Dist. YL Start PP Play Desc. End PP PPA
1 10 NU 19 .561 2y rush, Robinson .215 -.346
2 8 NU 21 .215 14y pass, Martinez-Stoll 1.757 1.542
1 10 NU 35 1.757 1y rush, Mills .924 -.833
2 9 NU 36 .924 5y penalty, no play .591 -.333
2 14 NU 31 .591 pass incomplete -.128 -.719
3 14 NU 31 -.128 17y pass, Martinez-Spielman 2.992 3.12
1 10 NU 48 2.992      

From that point, first-and-10 at its own 48 with two first downs under its belt, Nebraska upped the tempo forcing a South Alabama penalty, then followed it up with a 42-yard pass to Jack Stoll and hammered the ball into the end zone from there with three straight Dedrick Mills runs.

I remember thinking at the time that it was sort of a statistically improbable drive. The first two first-down plays went nowhere. Nebraska got out of second-and-long and third-and-long with two chunk plays. It felt like the sort of thing you could get away with against South Alabama but not the better teams on the schedule. It was just the first drive of the season, however.

But the Nebraska offense never really got untracked against South Alabama. It looked better, for the most part, for three straight games after that (turnovers excepted) but has since fallen off a cliff (while averaging one turnover per game). Which sent me back to that gut reaction to the opening drive.

It would be an oversimplification to call those fist six plays a harbinger of what was to come over the next six weeks. But with the benefit of having seen all of the plays that followed those first six, they weren't exactly an outlier either.

Specifically, the two meh first down gains. As we try to sort through why the Huskers' offense is struggling after a strong Year 1, I'm not sure that conversation can happen without focusing on what has happened so far on first down.

There are many ways to look at that, so let's start with the most basic way––yards per play. The 2019 offense is averaging 5.6 yards on first down (92nd), down from 6.4 last season (30th). That's an issue. The run game hasn't been the biggest culprit here. Nebraska in 2019 is averaging 4.36 yards per first-down rush (79th), down from 4.88 in 2018 (52nd). The bigger drop is in the passing game where the Huskers have gone from 8.32 yards per first-down pass attempt (48th) to 7.71 (78th). Put a pin in that for a second.

The interesting thing about this drop in yards per play on first down is that the drop in efficiency hasn't been quite as steep. The Huskers' success rate on first down in 2019 is 44.1%. That's still above the national average but down from 49.1% in 2018. That's a 10.2% decrease from 2018 compared to a 12.5% drop in yards per play. From a first-down efficiency standpoint, Nebraska is down but still decent compared to last season. Yards? A little more down, a little less decent.

Where the Huskers have cratered is in Predicted Points Added on first down. PPA is really an explosiveness measure. To drastically change the expected value of the next play, a team needs big gains. In 2018, Nebraska's offense was adding .122 predicted points per first-down play (22nd). On average, it was creating value for itself with not just consistent gains but sizable gains.

On average in 2019, the Huskers' first-down plays have decreased the predicted point value at the start of the drive. Nebraska's PPA on first down through seven games this season is -.031 (105th), a drop of 125% from last year.

You can see the impact that's having on Nebraska's offense by what happens on the downs that follow. Here are all three of the stats above, but for second and third downs as well as all plays.

Downs 19 PPA 18 PPA 19 SR 18 SR 19 YPP 18 YPP
1st -.031 .122 44.1% 49.1% 5.6 6.4
2nd .156 .346 40.1% 51.1% 5.6 7.3
3rd .516 .389 40.4% 37.6% 6.2 4.6
All .145 .233 42.0% 47.5% 5.7 6.3

First-down success is vital to every team, of course. That's just the way the game is built. A strong first-down gain sets up better situations on second and third downs, and, because the downs are sequential, most of the football a team will play will be on first down. Pretty simple.

But first-down strength appears to really matter to a Frost offense. Nebraska, for all of its impressive offensive numbers in 2018, wasn't very good on third down last year. It ranked 86th in conversion percentage. But at 6.4 yards per play on first down and 7.3 on second, the Huskers' weren't in many third-down situations (seventh-fewest nationally).

The Huskers' 109 third-down attempts this season are the third-most nationally. They're converting at a better clip, but that's still worse than not having to convert at all.

This all works fine as a partial explanation for why the Huskers' offense has struggled thus far, but does it provide any solutions? "Be better on first down" isn't much of one. How do you do that? That still comes down to all of the basic things Nebraska is presumably working on this week––blocking, route-running, overall technique.

But here's one more interesting difference to chew on. So far in 2019 Nebraska has run the ball 62.6% of the time on first down. That's the exact same run rate as the Huskers have overall, and it's heavy on the run for a Frost offense. The 2018 Huskers ran the ball 53.4% of the time overall and 55.3% on first down. The 2016 and 2017 UCF teams ran the ball 55.5% and 58.4% of the time on first down respectively and both ran it 54.1% of the time overall.

Why are the Huskers' so run heavy in 2019? That's going to require some additional investigation, but I'm guessing Nebraska's 8.8% sack rate (106th) might have something to do with it. All the wide receiver talk goes in here, too.

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