The Denver Broncos had a very simple formula to get back to the Super Bowl: banking on their elite defense to continue being elite. And contrary to concerns about possible regression, it stayed great. Denver, again, has the best defense in the NFL per Football Outsiders' DVOA metrics, which measure success rate on a play-by-play basis and are adjusted for quality of competition. Not quite as great as it was in 2015, but still stifling.
And yet, the Broncos enter Week 16 behind the Dolphins for the last wild card spot, with two tough games against Oakland and Kansas City remaining. How did their season go wrong?
Your first instinct might be to blame the passing game. The Broncos saw Peyton Manning retire, let Brock Osweiler walk, and addressed the quarterback position with first-round pick Paxton Lynch. But after finishing 25th in pass offense DVOA last year, this season, with unrenowned Trevor Siemian under center, they're in 23rd place through Week 15, and they're a net positive rather than a net negative. Yes, that's right—they're a bit better.
The real issue, unfortunately, is that the Broncos simply can't run the ball. At all. A staple of Gary Kubiak's best offenses in his time in Houston was to have the zone blocking scheme pick out great holes for his backs, who would then exploit them. Here's how this has generally worked out:
Gary Kubiak's Offenses in Rushing, by Year
In 2009, the Texans suffered through a terrible season of run-blocking. Running back Steve Slaton got hurt and was never the same player after his return. Scrap-heap guards Kasey Studdard and Chris White didn't integrate well into the Kubiak system. But in 2010, after bringing in free-agent guard Wade Smith, and giving guard Mike Brisiel a full-time job, things turned around in a hurry. Arian Foster ran all over the league in 2010 after a little Kubiak fixing.
So it was natural to look at Denver's 2015 season and assume that things would turn around much the same way. Kubiak rushing offenses don't tend to stay bad this long. But the Denver offensive line hasn't been on the same page all season. As much as losing starting back C.J. Anderson to injury hurt the team, it wasn't like he'd been appreciably better than the other backs.
Denver's Rushing by Back, 2016
The way the Denver backfield played out, in actuality, is pretty simple: whoever Denver's change-of-pace back has been, he's done fine. You can see this in Devontae Booker's rushing lines before he became a starter: his box score had lines like nine carries for 46 yards, or five carries for 46 yards. You can see them in Kapri Bibbs' time as a change-of-pace back for Booker, when he often looked like the more impressive back.
The Broncos running game is broken in base personnel. On first and second down, when Denver runs their DVOA on those plays is -27.1 percent and -20.8 percent, respectively. On a weekly basis, Trevor Siemian has been set up to fail because this offense can't stay on Kubiak's preferred schedule.
A lot of that blame needs to fall on the offensive line. Outside of center Matt Paradis, who has been a bit of a find, the Broncos have been hard-pressed to find a good run blocker on the line. Denver's got some big names and recent high-round draft picks on hand, but the results aren't there. Left tackle Russell Okung is a better blind-side protector than a zone-blocking scheme puller, but between second-round tackle Ty Sambrailo and free-agent signee Donald Stevenson, the Broncos have zero good right tackles. Sambrailo in particular has been dreadful when healthy enough to suit up.
Also making up this line are guard Max Garcia (2015, fourth-round pick) and guard Michael Schofield (2014, third-round pick). Between those two and Sambarilo, this is a lot of draft capital that simply isn't playing well.
A zone-blocking scheme takes time and trust. Unlike a typical man-on-man scheme, the familiarity of the players matters in zone because you are asking them to play together. Combo blocks where one lineman helps another before going to the next level are pretty common.
So maybe we should have seen this coming when Denver brought in two free agents this off-season and fielded a line full of guys who have barely played with each other. Paradis and Schofield are the only players who saw more than 600 snaps on last year's team.
Still, it's galling to look at this defense and imagine that, of all people, Gary Kubiak couldn't even craft a running game to work with it. Maybe they get hot over the last few weeks of the season, and the line (finally) starts to gel enough to get something going behind Justin Forsett, Kubiak's main back in Baltimore in 2014. If they don't, Denver will be sitting at home in January instead of defending the Super Bowl.
All because they couldn't find five guys that could block together adequately.
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