For Sunday's AFC Championship Game, the Denver Broncos will be missing two key defenders who played in the 34-31 loss to New England in Week 12. Linebacker Von Miller tore his ACL in Week 16, while cornerback Chris Harris tore his ACL in last week's win over the Chargers. What kind of impact might the loss of each player have in the rematch? How good exactly have the Broncos been with and without Miller, and which defenders might the Broncos be forced to rely upon in Harris' absence?
The answers to those questions may determine which team pushes through to the Super Bowl.
The good news is that by this point of the season the Broncos should be more than used to playing without Miller. Between his six-game suspension to start the year and the torn ACL, Sunday will be the ninth game the Broncos have played without their star third-year pass rusher, which will match the number of games he actually suited up for this season.
That does not mean the Broncos have played well without Miller. While they took down the Chargers, by Football Outsiders' DVOA ratings ( explained here), Denver's defensive DVOA without Miller is 10.8 percent, which would have ranked 27th over the course of the season. Their actual full-season DVOA was minus-0.2 percent, good for 15th, so it is apparent Miller's presence made a significant difference.
The good news is the Broncos still played excellent run defense without Miller. In the games he missed, they actually had a better run defense DVOA (minus-20.6 percent) than they did with him in the lineup (minus-11.4 percent). That included limiting the Patriots in the first meeting to only 116 yards on 29 handoffs, plus forcing fumbles by both Stevan Ridley and LeGarrette Blount that earned them quick trips to the bench. The Broncos' run defense also played well against the Chargers last week, recording a DVOA of minus-31.2 percent.
It is against the pass where the Broncos have struggled without Miller. With him, they had a pass defense DVOA of minus-9.9 percent, which would have ranked sixth for the season. In the games he has not played, their pass defense DVOA is 28.1 percent, worst in the league.
Given that Miller had 18.5 sacks in 2012, the obvious answer is that without him, the pass rush is lacking. A look at sack data, however, suggests this is not the case. The Broncos' Adjusted Sack Rate, which accounts for opportunities and the quality of opposing offenses, was 6.7 percent with Miller in the lineup and 6.3 percent without him. Given that Adjusted Sack Rates around the league ranged from 5.3 percent to 9.5 percent, that is a virtually indistinguishable change.
The Broncos also hurried the opposing passer slightly less frequently with Miller in the lineup, even though they brought five or more rushers more often with him active. Whatever has caused the Denver pass defense to play worse without Miller seems to be completely in the coverage and how opposing teams attack the Broncos, not in a decline from the pass rush.
Wherever and whenever, Chris Harris was a key part of that Broncos coverage. That was especially true in the areas the Patriots attack frequently.