A pass-rushing phenomenon with no obvious replacement on the roster, Miller has combined with quarterback Peyton Manning to give the Broncos a one-two punch worthy of a Super Bowl champion.
However, it's now looking probable that the Broncos will have to work through the absence of their best defensive player for the first quarter of next season's schedule due to a suspension from violating his team's substance abuse policy. According to Lindsay H. Jones of USA Today, Miller is appealing and claiming innocence (via Twitter).
Denver is somewhat fortunate that a suspension will come during the first four games and not later in the season, but Miller's potential absence will create a very difficult opening stanza for the defending AFC West champions in 2013.
According to AdvancedNFLStats.com, Miller finished 2012 as the top linebacker in terms of Positive Expected Points Added (+EPA), which measures a defensive player's complete impact in terms of playmaking ability. His final score of 78.9 trumped second-place linebacker LaMarr Woodley by over 14 points, and trailed only J.J. Watt of the Houston Texans for the overall NFL lead.
Pro Football Focus (subscription required) agreed, as Miller's final regular-season grade of 78.5 led all linebackers and was bested only by Watt. In fact, Miller's grade finished over 60 points higher than the next 4-3 outside linebacker. And in the five years PFF has graded players, no one at Miller's position has come within 50 points of his 2012 tally.
Overall, and including postseason games, Miller produced 93 of the Broncos' 295 total quarterback pressures last season, per PFF (subscription required). His 58 "stops," or a tackle that constitutes an offensive failure, was a team-high, and he incredibly missed only three tackles all season.
Proof of his dominance from the linebacker position was just as evident in the surface stats.
Miller provided 18.5 sacks, which trailed only Watt (20.5) and Aldon Smith (19.5) for the league lead but set a new franchise record. His six forced fumbles ranked third in the NFL, while his 28 tackles for a loss were second.
The Broncos must now attempt to replace his production with players already on the roster.
Good luck with that.
Already robbed from said roster is Elvis Dumervil, who took his 63.5 career sacks (fourth all-time in Broncos history) to the Super Bowl champion Ravens this offseason. In 2012, Dumervil produced 11 sacks and six forced fumbles as the Robin to Miller's Batman.
Also, consider this: When combining Miller's suspension with Dumervil's departure, the Broncos are now looking at playing the first four games of next season without 155 of their 295 quarterback pressures from 2012.
There's no addition or "trickeration" in the world that can help the Broncos replace that kind of pass-rushing productivity.
Denver will simply have to lean on the likes of Shaun Phillips, a veteran who had 9.5 sacks for the San Diego Chargers last season; Quanterus Smith, a rookie coming off ACL surgery; and Nate Irving, a potential starter at middle linebacker who can play on the strong side. Defensive end Derek Wolfe, linebacker Wesley Woodward and defensive tackle Sylvester Williams will also need to help pick up the slack in Miller's absence.
There is talent and potential in the names above, but also a lot of question marks.
Phillips, 32, has always been a volume pass-rusher who struggles to provide consistent overall impact. According to PFF, Phillips graded out as the second-worst 3-4 outside linebacker in football last season.
His 9.5 sacks were mostly a mirage, clouded by the fact that his 485 pass-rushing snaps provided just 38 total pressures. In comparison, Miller tallied 86 pressures over 436 regular-season pass-rushing snaps.
Smith is an intriguing athlete after leading the NCAA in sacks through 10 games last season. Even after tearing his ACL, he still ended up leading the nation in sacks per game with 1.25. However, his injury may mean he'll only be effective in obvious passing situations later in the season.
Irving may wind up being the starter at middle linebacker, but he does have experience playing on Miller's strong side. Yet he's nowhere near the pass-rusher Miller is, and his overall experience as a third-year player is limited.
The question becomes: Can the Broncos play winning football on the defensive side without Miller and Dumervil?
As John Clayton of ESPN smartly pointed out, the Broncos have successfully used a specific formula since Manning arrived on the scene last season. First get a lead via the offense, then protect it with an attacking defense led by dominant pass-rushers.
Such a blueprint has worked for the Broncos, as the defense improved from No. 18 in Football Outsiders' defensive efficiency rankings in 2011 to No. 5 last season. The biggest jump in 2012 came against the pass, where the Broncos increased their sack total by 12 and took off nearly 600 yards of passing offense.
Unless the offense can make up the difference Miller provides on the defensive side with a bevy of points, the possibility of a 2-2 start looms large.
Not having a strong pass rush could mean big trouble against quarterbacks like Joe Flacco and Eli Manning.
A team quarterbacked by Peyton Manning can win on any given Sunday, and it'd be unfair to say the Broncos are incapable of fighting through the loss of their best defensive player for just four of 16 games. This is a talented football team that should be playing well into January.
However, Miller's likely absence has created the possibility of Denver having to climb out of an early-season hole. He's simply too talented and defensively vital to assume the Broncos' chances of winning in the first four weeks won't be significantly reduced.