Looking back at 2017: Is the Niners defense better this year?

Everyone has talked nonstop about how the Niner’s season turned around once Jimmy Garappolo showed up and the team won 5 straight games. What seems to be lost in the shuffle in all the QB hype, is that during the season the team significantly overhauled the defense.

I think there is a case to be made that the defensive improvements arrived before those on offense. Also the team is poised to build on those improvements that happened during the year in 2017.

The question on everyone’s lips seems to be:

Will the Niners defense be better than last year?

Yes, by a lot. Let’s take a look at how I got to that conclusion.

In general when comparing teams year to year each year’s team is assumed to be static. For the Niners defense last year that assumption is way off the mark.

The defense that ended the year was waaaaay different than the defense that began the year. It changed all year long, until it finally settled down in the last 6 games or so. The defense that ended the year was much much better than the defense that started the year.

So to improve on last year’s overall defensive numbers is relatively straightforward. All the team needs to do is replicate the defense that finished the year. But I think the team has made more improvement beyond just replicating the 2017 year end defense.

In short the defense in 2018 should be much much better — better compared to where they ended their year, better than the full year numbers, and especially better compared to where the defense started last year.

A Quick Defensive Recap of 2017 on D: Repairing the Car while Driving

The Niners made an unusually large number of roster changes on defense during the year, prompted by a combination of ineffective play, maturation of rookies, and injuries.

For the first quarter of the season plus a bit (5 games) these players were starters and played a lot of snaps:

By mid season these players were basically gone. Armstrong was with the team till game 10, but had no meaningful snaps on defense after mid season. When you look at full season numbers, remember these players were big contributors to the defense to start the year. Those players were roughly a third of the defense for the first 5 weeks.

Mid season Revolving Door

In the middle of the season players came and went especially on the defensive line: Xavier Cooper, Datone Jones, Tony McDaniel, Leger Douzable. All these player came in off the street and played a fair bit. Then they were let go or benched.

Other players also came in off the street and played smaller roles on defense, primarily in the secondary: Leon Hall and Antone Exum. Hall in particular was a consistent modest contributor down the stretch at the end of the year in the secondary.

The MASH Unit

Meanwhile during the year, these starters exited with injuries: Armstead* (missed 10 games), Foster (missed 6 games), Ward* (9 games), Tartt*, (7 games), Reid (3 games), Thomas (2 games)

* ended season on IR

Also projected starter Malcolm Smith was also lost to IR for the season during preseason

Plus, these contributing players missed half the year or more due to injury:

Ronald Blair (10 games), Tank Carradine (8 games)

The injury bug hit the defense hard in 2017 and despite that, the overall defense improved down the stretch.

Reinforcements Arrive

Two waiver claim defensive linemen arrived late in the year and seemed to make an impact: Cassius Marsh and Sheldon Day

Both quickly earned significant snaps. Both are signed for 2018 and beyond, Marsh via a significant contract extension.

After these two arrived and with the coincident emergence of key rookie draftees Witherspoon and Colbert in the defensive backfield, and the generally improved play of Coyle at LB along side Foster who returned mid season from injury — the defense improved a lot.

Let’s take a look at some data

Running the Numbers

In the last six games the defense yield just one 100+ rushing game (Just barely giving up 102 to the Rams in the 34-13 year end rout). In contrast the Niners gave up over 100 yards rushing in 8 out of the first 10 games. Sometimes a lot more. That seems significant to me.

In addition each of the last six games the Niners defense held its opponent under their season average in yards per carry. Here are the rush totals for the last six games, opponents season average yards per carry in ():

  • 3.00 yd/car, 30 car 90 yds vs Seahawks (4.0)
  • 3.36 yd/car, 19 car 62 yds vs Bears (4.2)
  • 3.91 yd/car, 23 car 90 yds vs Texans (4.1)
  • 3.21 yd/car 28 car 90 yds vs Titans (4.1)
  • 3.29 yd/car 28 car 92 yds vs Jaguars (4.3)
  • 3.92 yd/car 26 car 102 yds vs Rams (4.3)

That seems to be pretty consistent performance. Let’s look at the totals:

  • Total Last 6 games: 3.4 yd/car, 154 car 526 yd
  • Total First 10 games: 4.9 yd/car, 337 car 1335 yd
  • Total for the year: 3.8 yd/car, 491 car 1861 yds

This seems like a huge difference to me. As a reference point, the best run defense in the league for the year was Denver who held opponents to 3.3 yd/car all year long Cleveland was second at 3.4.

So if people are asking will the run defense be better? Maybe it already is.

Down and Dirty

This improved run defense seem to carry over into another relative statistical week spot for the Niners defense, third down conversions. Overall for the year, the Niners were not very good. But in the last 6 games of the year the team was significantly better. That’s not surprising really. Better run defense leads to more favorable down and distance which makes conversions harder. Overall for the year the Niners ranked 30th, allowing a 3rd down conversion percentage of 43.0%. Here’s the data on 3rd down conversions for the last 6 games:

  • 5-13 Seahawks
  • 5-10 Bears
  • 3-13 Texans
  • 6-12 Titans
  • 5-13 Jaguars
  • 5-15 Rams

Again this performance seems consistently solid with some variation but not huge, in two games they allowed 50%. Here are the totals for the last 6 games compared to the first 10 games

  • Last 6 games 3rd down conversions allowed 29-76 38.2%
  • First 10 games 66-145 45.5%

For some context let’s compare to to the league wide numbers. Had the team maintained it 45.5% rate from its first 10 games, it would have dropped to 31st in the league, just below Indy at 44.7%, but not as bad as the league worst Tampa at 48.1%. So pretty awful. Conversely, if the Niners had managed the same rate for the year as the last 6 games, the team would have landed in the middle of the pack at 17th just behind the Seahawks and Lions 38.1%.

The performance improvement on 3rd down is not nearly as big as in the run defense, but still seems significant.

Offseason Changes So Far

The Niners have not rested on their laurels and continued to make improvements on defense during the off season. A big thrust of the off season was to improve the secondary. The team is looking for a significant upgrade to Dontae Johnson.

That’s a big deal. As much as people may not like Dontae Johnson, he played a lot last year, 1026 snaps (91.2% of all defensive plays). He played more snaps on defense than any other player. So upgrading his spot is one of the biggest upgrades the team can make, an upgrade that effects nearly every single play on defense. The next closest player defense in snap count was Buckner at 836 snaps or 76.7% of all snaps on defense.

The off-season upgrade at CB comes in the form of a big time FA Richard Sherman, and a super athletic draft pick Tarvarius Moore. This combination doesn’t have to be great to have big impact. They just need to be better than Dontae Johnson, who had a PFF grade of 50.3. That is a really low number for a player that played as much a Johnson did. The upgrade here could help the 3rd down conversion number even more.

The other area on defense that received significant attention in the of season was Mike/Will linebacker. When Rueben Foster’s fate was uncertain the team went a little over kill, resigning Mark Nzeocha and Brock Coyle, signing vet Korey Toomer, and drafting Fred Warner in round 3. That’s all on top of last year’s expected starter Malcom Smith returning from injury. This competition behind Foster will be fierce and deep. The team will end up with very solid depth here however it turns out. As a result the Niners can handle Foster’s two game suspension with aplomb. This also may mean run defense improves even more.

The last area worth a mention on defense is pass rush. The team seemed to not do a lot. I think part of that is that there wasn’t much to do. There weren’t impressive pass rush FAs and the draft was super thin in pass rushers. So I think they did the best they could for now and will continue to seek upgrades through signing cap casualties or trades.

There been a lot conversation around why the team let Elvis Dumervil go. (I posted elsewhere in comments but I’ll repost part of it here again). Basically when Marsh showed up he outplayed Dumervil.

Once he came aboard he earned more snaps than Dumervil and produced the same number of sacks. Marsh also contributed more tackles. Here’s the data:

  • Marsh 189 snaps, 10 tackles, 1 assists, 2 sacks
  • Dumervil 147 snaps, 4 Tackles, 2 assists, 2 sacks

So, 29% more snaps for Marsh but 150% more tackles against identical competition and the same number of sacks.

I can see why Marsh got extended and the aging Dumervil was not resigned. Marsh has looked great in camp so far too.

I also happen to like the FA signing of Jeremiah Attaochu. I know I’m biased though, as I really liked him as a possible draft pick out of Georgia Tech. That said, Attaochu is young athletic and has a great motor. He also seems to have a new attitude after getting cut from SD. He’s not going to play a lot, maybe 20-30 snaps a game, but he’s explosive and could shine. He might play more if he can play SAM and push Harold. Even still his impact could be significant and he also plays the run reasonably well unlike Dumervil.

Remaining issue on Defense to Watch

The hidden issue of the improved 3rd down performance was a league worst performance on 4th down. The team allowed whopping 83.3% to be converted. In the last six games, this number was also 83.3%, same as the first 10 games. If the team want to be a consistent winner, they need to post respectable 4th down conversion numbers. Last year numbers were crazy bad. Something to watch as the season unfolds. This seems solvable. But until it shows up as solved, it remains a concern.

The Siren Song of the Snake SSS

So the big caveat in all of this projection is SSS or small sample size.

I’ve projected a lot of things based on just a few games or snaps and those small samples may be an anomalies that won’t be repeated. I get that. On the other hand, the sample sizes for the most part are still decent (6 games not 2) and some of the trends are very strong. So while the projection may not be wrong, the outcome may have a lot of variation or rather lower confidence levels.

The other big complication is a bit of a chicken and egg problem. The team won its last 5 including a big surge on the part of the offense. Given this, the last 6 game numbers are highly likely to be better. Did they team win because they produced better numbers? Or did they produce better numbers because they won? The honest answer is I don’t know. My intuition looking at the data tells me the defense arrived first and played well enough to win the last 6 games, had the offense held up its end against the Seahawks.

Despite these data issues and uncertainty,I expect the overall defense to be better that last year, even if that’s only as good as the end of last year.

Looking Ahead

I’m very optimistic about the defense overall compared to last year. Most of the big changes were actually made during the season last year. That gives me more confidence around these changes compared to the more recent offseason ones.Then this year they literally poured resources into the biggest weakness that was immediately fixable — pass coverage. The team took not just one swing at upgrading pass defense, it took several.

I expect a big leap. They won’t have to do major tinkering with the defense during the year. They might do some tinkering with pass rushers but nothing like the wholesale repeated changes they made during the season last year. I think the defense is poised make big step forward that will look even bigger compared to last years funky mixed numbers. They should be a top 10 defense or close, this year — maybe bit better if they stay heathy.

Curious to hear your thoughts in the comments.

This is a FanPost and does not necessarily reflect the views of Niners Nation's writers or editors. It does reflect the views of this particular fan though, which is as important as the views of Niners Nation's writers or editors.