Need another reason to back away from Lions RBs? Well, stick around to the end of this article and you’ll get one. (Or you could cheat and skip over the juicy middle … but why would you do that?)
Last week, I broke down recent historical fantasy points allowed stats for QB defenses and projected a 2018 strength of schedule for fantasy passers. Now we turn to the guys lining up behind them, the RBs that have gone back to dominating the top of fantasy football draft boards.
Just like last time, let’s start in the past …
Effects on RB Scoring
I looked back over RB points (PPR) allowed every season since 2002, when the league expanded to 32 teams. Just like at QB, we saw the impact gaps grow at the top and bottom of the rankings.
The 1st column in the table below indicates the average difference between the defense in that ranking spot and the median points allowed to fantasy RBs over the same span (2002-2017). The 2nd column shows the gap between each consecutive pair of ranking spots (in percentage points; not true percentages).
As you can see, gaps of generally less than 1.5 percentage points through the middle give way to larger splits at the top and bottom of the rankings. This proved true annually, too. The tougher the RB defense, the more drastic the impact on RB scoring. On the flipside, the easier your matchup, the more drastic your backfield scoring boost.
On average, we also found the top 9 and bottom 9 RB defenses affecting opponent scoring by 10+% vs. the league median. So I used those ranges to gauge potential impact when compiling the 2018 strength-of-schedule rankings I’ll get to in a few minutes.
What Makes a Tough RB Defense?
Before projecting the good and bad defenses for 2018, I wanted to find out what tends to impact points allowed the most. Even in this era of increased passing, you probably won’t be surprised to learn that rushing yards and rushing TDs drive these rankings.
The chart above displays the correlation between the 6 primary RB stat categories and fantasy points allowed, by year. As you can see, each color represents a different stat. And we’re looking for correlations closest to 1.0.
From 2000 through last season, rushing TDs and rushing yards each sport a median correlation of 0.774. No other stat tested beat 0.614.
Obviously, all of these categories contribute to RB fantasy scoring, but we’re looking for what we can expect to have the most impact so we know where to look when we project. Yards and TDs are the places to look.
The problem with TDs, of course, is that they’re difficult to predict. Over the same span, TDs consistently fall short of a 0.6 correlation with rushing yardage -- at times short of 0.5. What’s that mean? Just because a defense gives up a lot of yards on the ground does not necessarily mean that it also ranks among the most susceptible to rushing TDs. Same deal with the correlation between rushing attempts and TDs. So, just because a defense faces more carries than most of the league, we can’t necessarily assume that D will allow more of those to reach the end zone.
Rushing yards and rushing attempts, on the other hand, have shown a perennial correlation of 0.75 or better in recent seasons.
That makes sense. We would assume that those defenses facing more rushing attempts would allow more rushing yards. And we’d be right.