Just a few days now until the Minnesota Vikings travel to Ford Field for a showdown with the Detroit Lions for the NFC North Division title, the top seed in the NFC playoffs, and all that goes with that. Given the high-profile nature of the game, there are no shortage of national previews of the game, and I thought I’d include some of them here.

But first a high-level analysis of what’s changed with the Vikings and Lions since their first matchup in week seven.

What’s Changed Since Week Seven

The biggest change since week seven has been the injuries the Lions have suffered, particularly defensively. Offensively the Lions are as strong as ever, but defensively the bottom has fallen out.

From week 1-12, the Lions’ defensive EPA/play allowed was second-best in the league behind the Vikings. But from week 13-17, the Lions’ defensive EPA/play allowed has been the worst in the NFL. That’s reflected in the Lions’ Rolling EPA chart below.

As you can see, just past play number 800 for the season (roughly week 13), the Lions’ defensive EPA (gray dotted line) begins to go up dramatically, which means their defensive efficiency was rapidly getting worse (negative EPA numbers are better defensively). Offensively there was a less dramatic dip before it returned to its previous level. But you can see from the solid blue line how the Lions’ net EPA declined dramatically shortly after play number 800 and has remained near zero since.

The Lions defensive decline is reflected in their defensive DVOA metric as well.

Like defensive EPA, defensive DVOA numbers are better when they’re negative. As you can see, the Lions defense since week 13 is dramatically different in DVOA terms than the first twelve weeks of the season. DVOA is meant to be a percentage relative to “average” so the Lions defense has gone from significantly better than average over the first twelve weeks of the season to significantly below average since then.

The decline of the Lions’ defense also shows up in their Total DVOA metric, similar to their Net EPA metric.

As you can see, the Lions’ Total DVOA is dramatically lower since week 13 compared to weeks 1-12. In fact, the Lions’ average game Total DVOA was 48.7% from weeks 1-12, but just 4.7% since week 13.

The Vikings, by contrast have shown a different dynamic over the course of the season in EPA and DVOA terms.

From the Vikings’ Rolling EPA chart above, you can see they started the season strong, particularly defensively, then dropped dramatically before returning to near their early season highs and have more or less remained at that level. However, you’ll notice that offensive EPA has shown a strong positive trendline since its low point early in the season while the defense has been more up and down since the strong start to the season.

Looking at the Vikings’ week-to-week performance in Total DVOA terms below, if you break up the season into fourths, the first fourth of the season was very strong, the second mediocre, the third building back, and the fourth more varied but continuing an upward trend.

Overall, the Vikings enter week 18 coming off one of their best games in Total DVOA terms against the Packers and trending in a positive direction in Net EPA terms. Meanwhile the Lions enter week 18 at a low point in Net EPA and have become something similar to the Bengals in the sense that they need their offense to carry the team as the defense is limping into this game bruised and battered after suffering so many injuries.

In the week seven matchup at US Bank stadium, the Vikings punted three times, had two drives end with the half and game, and had three field goals in addition to two touchdowns and an interception.

Meanwhile the Vikings’ defense forced the Lions to punt four times, had a 4th down stop, a fumble returned for a touchdown, while giving up four touchdowns and a field goal.

My guess is that if the Vikings’ defense can have a similar performance (forcing four punts, a 4th down stop and a turnover) the Vikings’ offense will be able to put up more points than week seven and lead to a Vikings’ victory Sunday night.

National Vikings-Lions Previews

Check the Mic (Steve Palazzolo & Sam Monson, formerly with PFF)

FTN (Aaron Schatz the DVOA Guy and Mike Tanier)

PFF

Pro Football Talk

Clean Pocket

Mina Kimes – ESPN