The Denver Broncos have an offense that is great, but their defense has taken a step back from a year ago. Who needs defense when the offense is scoring more points in a single game than some teams have scored all season, right?
Through the first four games, the Broncos looked like they could be one of the greatest teams ever, but they won't get even close if their defense doesn't play better than it did against the Dallas Cowboys. As good as the offense has played, if they want to win in the playoffs, they might want to get more out of the defense.
The good news for the Broncos is that injured starting cornerback Champ Bailey is nearing a return and could play this week against the Jacksonville Jaguars, and pass-rusher Von Miller's six-game suspension ends next Monday.
It's obvious that the Broncos should improve when they get those two players back. But by how much?
Through five games, the Broncos are allowing a league-high 8.8 yards per attempt and 14.7 yards per completion with a sack percentage of 6.7 and a touchdown percentage of 5.3.
Both numbers are both well below the league average. That's not the kind of production you would expect to see from a defense that should be able to take advantage of desperate teams that have fallen behind.
Measuring the Impact
The Broncos have scored 230 points through five games, the most ever through the first five weeks of NFL season. But they have also allowed a most-ever 1,735 passing yards. With two NFL marks in direct opposition to each other, one might assume one is a byproduct of the other, but that explanation doesn't hold true when you look at the other great offenses in the last 20 years.
The 2000 St. Louis Rams that went 10-6 and scored 217 points through five games (second all time) allowed 1,352 passing yards. Five of the Rams' six losses had a lot to do with that lackluster defense. The 2007 New England Patriots went 16-0 but allowed only 886 passing yards through five games, which explains why they were undefeated in the regular season.
It's worth noting that eight of the top 10 teams that have allowed the most passing yards in NFL history through five games have come since 2005—including three teams in 2013. The NFL continues to evolve into a pass-heavy league, so some of the extra yards passing that Denver has surrendered are probably part of the normal evolution of the game, combined with playing with a huge lead in four out of the five games.
One might point to the Broncos allowing just a 59.8 percent completion rate as a positive, but that means they are allowing an especially large number of big plays in the passing game. You would think that the team would be allowing a higher completion rate and fewer yards per catch trying to protect leads, not the other way around.
According to Advanced NFL Stats, the Broncos have the worst defensive pass EPA (Expected Points Added) in the NFL at plus-64.2. Even when we look at EPA per play to accommodate the Broncos defense seeing more pass attempts, they still rank last in the NFL. Last year the Broncos ranked fifth in both defensive pass EPA and EPA per play.
To put it in perspective, the difference from last year to this year in defensive pass EPA per game is plus-13.2 points (note that a positive EPA is bad for a defense) and the difference in offensive pass EPA is plus-10.5. The run defense has actually improved slightly over last year, according to EPA, and the running game on offense is the most improved.
Maybe the improved running game—and not just the passing game—is why the Broncos have been scoring so many points. It makes sense because a more productive running game would put the offense in better position to do things, like converting on third down.
If we look at another advanced stat called WPA (Win Probability Added) for the pass defense, the Broncos are a little better but still rank 27th—a big drop from last year when they ranked second. Obviously, the Broncos miss Miller and Bailey on defense.
Supporting Cast and Replacement Production
The Broncos should be able to replicate their production with Miller and Bailey back in the lineup, if not improve upon it. That seems crazy right now, but all of the other changes the Broncos made defensively are paying dividends.
Shaun Phillips has been filling in for Miller as a pass-rusher, but he can help replace for the loss of Elvis Dumervil once Miller returns. Having two quality pass-rushers should really help Denver's secondary.
Terrance Knighton appears to be an upgrade over Justin Bannan at defensive tackle, which has been reflected in the defense allowing 3.3 yards per rush. Even though Denver's weekly offensive barrage has forced opponents to abandon the run early, when opposing offenses have tried to run the ball, they have not had much success.
Danny Trevathan is now a starting linebacker, and he's playing well. Duke Ihenacho is now the starting strong safety, and he's being asked to do a lot of different things in run support and pass coverage for a first-year starter. And he's still playing well. Normally Ihenacho would have Bailey on his side of the field to take some of the pressure off him in pass coverage.
The other big addition was Dominique Rodgers-Cromartie at cornerback. Last season, the Broncos signed Tracy Porter, but after he experienced dizziness, he was replaced by Tony Carter. Rodgers-Cromartie was Carter's replacement, but the injury to Bailey has forced Carter back into a starting role.
If a player comes in and plays well for an injured starter, the loss of that starter isn't as severe. Coaches call this the "next man up" approach, even if they know there is a big drop from one player to the next. If Carter had come in and played well, maybe Bailey's loss wouldn't be as severe.
Unfortunately for the Broncos, that hasn't been the case.
Carter is Denver's worst defender in coverage by a wide margin, according to ProFootballFocus (subscription required), which gave the Broncos corner a minus-6.2 coverage grade. ProFootballFocus has graded only four cornerbacks worse than Carter out of 104 CBs who have played at least 25 percent of their team's snaps.
Apparently, the Broncos knew what they were doing in the offseason. Many of the team's additions don't appear to be impact players, though all of them were upgrades at their positions. The Broncos may have lacked depth, but it's not as if there are players out there who could realistically replace Miller and Bailey without the defense experiencing a noticeable drop-off.
More Miller Time
If Miller is able to step right in and make the same kind of impact he did last year—and there is no reason to believe otherwise—the Broncos pass rush is going to go from average to elite overnight. An elite pass rush will help the entire pass defense.
Miller had 19 sacks, 15 quarterback hits and 52 quarterback pressures in 470 pass rush attempts last year, according to ProFootballFocus, which translates to at least five total pressures (sacks, hits and hurries) per game. Miller was probably the most productive pure pass-rusher in the NFL last season, and he should be well rested when he returns in 2013.
Last season, 559 passes were attempted against the Broncos and Miller rushed the quarterback 84.1 percent of the time. The 559 passes attempted against Denver last season translates into 34.9 attempts per game, which is 6.9 attempts per game fewer than this season, an increase in pass attempts of 19.8 percent.
If we adjust Miller's production—assuming opponents will be passing more because the Bronco offense will continue to score an absurd amount of points—Miller is likely to gain at least one more sack, hit or hurry per game. That might not seem like much, but six or seven total pressures per game from one player is huge.
Adding a great pass rush alone should mean more tasty treats for the secondary, but adding a cornerback like Bailey is like adding a little Irish Cream to coffee—it gives it an extra kick.
Bailey was still one of the best cornerbacks in football last year, and he was rarely targeted. According to ProFootballFocus, Bailey was targeted once every 7.9 snaps in pass coverage and only allowed a reception every 14.6 coverage snaps. (Coincidentally, it is the exact same rate that Rodgers-Cromartie has posted so far this season.)
Carter is being targeted once every 6.0 coverage snaps this season and is allowing a reception every 10.2 snaps, which is similar to his numbers last year. The big difference is that teams are passing more, and the Broncos defense is applying a lot less pressure on the quarterback.
With Rodgers-Cromartie, Bailey and Chris Harris at cornerback, it's going to be very hard on opposing quarterbacks to find openings, and it will only be harder if Miller is breathing down their necks. That was the Broncos plan all along, but it was derailed by Miller's suspension and Bailey's foot injury.
Miller and Bailey are the two best players on Denver's defense, so to be missing them for about a third of the season has hurt. With Miller and Bailey the Broncos defense could return to last season's form or better, which would be worth around 13.3 EPA per game.
The defense's stated goal is to hold opponents to 17 points or fewer, according to Andrew Mason of DenverBroncos.com, something they have failed to do so far this season. The Broncos have allowed 27.8 points per game, a number that is obviously skewed after giving up 48 to the Cowboys.
However, take off the 13.3 EPA from the 27.8 points per game allowed, and the Broncos would make their goal by allowing only about 14.5 points per game—assuming all else remains the same. The third-ranked defense in the NFL this season in points allowed per game has allowed 14.5 points per game, so that gives you some idea of how good the Broncos need to be defensively.
It's really not that crazy to assume this is the type of production we will see out of the defense once Miller and Bailey return. A very similar defense with the same coordinator ranked fourth in points allowed last season (18.1).
If the Broncos can produce up to that standard for the final 11 games, they would finish the year having allowed 17.75 points per game—just above their stated goal. That's still an improvement over last season, despite Miller and Bailey having missed 11 games and counting.
When you add a top-five defense to a top-one offense, you get a team that might not lose the rest of the year. Right now the Broncos look beatable, but that's all going to change in the next couple of weeks.
The Broncos, with Miller and Bailey rejoining the fold, could be remembered as one of the best NFL teams ever. But without them, they are an unbalanced team that looks beatable under the right circumstances.