Ronald Darby (lateral oriented anterior dominant) is an interesting player to discuss– from a biomechanical perspective, of the players I’ve studied closely, he reminds me most of John Brown (WR). Both players are very efficient in a wide variety of biomechanical areas, but with full development/ efficiency in none. While Brown is more thoracic oriented and Darby is more lumbar oriented, in both cases these players are capable of playing at very high levels while fully healthy. However, their fascial systems– as efficient as they are when fully healthy– can best be described as “butter scraped over too much toast”. Meaning that in order to keep so many areas efficient at once (rather than favoring certain ones at the expense of others, like most players), their entire fascial system is very tight. And much like a finely-tuned performance car, little things (and occasionally big things) can and do go wrong, often resulting in performance that is far from peak.
If there is an upside to this signing (besides the obvious high-level play that accompanies full health) it’s in the timing– Darby is currently 27 and smack dab in the middle of his peak. The late twenties is the most stable period for the biomechanical system– until age 25 it is expanding (sometimes rapidly), and after age 30 it contracts (also sometimes rapidly), but during the late twenties the system reaches a stability that is often beneficial to tightly-wired players like Brown and Darby (since contracting or expanding a tightly wired system is a difficult balancing act). Darby is roughly the same age as John Brown when Brown signed his similar contract with the Bills in 2019, and I think on balance the Bills were happy with that signing. They got roughly 20 games of very high level play, with a smattering more of Brown playing reasonably effectively through injury (and a few more as a decoy), and when he was healthy he dramatically improved the output of their offense. If we see similar returns from Darby (20-ish fully healthy games played at a pro bowl level) over the first two years of his contract, I think this signing will be a success considering how much he will improve the level of the defense when he is at his best.
As for his role, Darby is an excellent runner, capable of staying with very speedy receivers all the way down the field (superlative lumbar efficiency when fully healthy). As such he is likely to play Fangio’s ‘matchup’ CB, who ends up tasked with covering the opposing teams’ best/ fastest receiver either in off-man or zone coverage. He shows both excellent long speed and fast closing speed, and though his somewhat subpar thoracic efficiency translates to somewhat weak tackling and poor ability to corral interceptions, he is nevertheless a very willing tackler (even in run support, unlike Bouye), and does an excellent job getting his arms in position to defend passes. Overall, a tightly wound but very efficient athlete (when fully healthy), who has often played through nagging injuries in his career, and who will hopefully maintain excellent health for the duration of his athletic peak in Denver.
While Ronald Darby is efficient but not fully developed, Kyle Fuller (lateral oriented anterior dominant) is very well developed (no apparent red flags for injury), but is decreasing in efficiency. Although it’s possible that Fuller was playing through an injury that I was unable to pinpoint in my time studying him, Fuller’s efficiency (particularly posterior) noticeably declined for the 2020 season. Fuller remained a physical and instinctual defender, but his ability to lock up opposing receivers (particularly down the field) fell substantially from his earlier peaks, and his long speed in particular appeared diminished. Although Fuller remained an excellent tackler and a quick-reacting zone cover in the near- intermediate areas of the field (showing particular aptitude for run support and sniffing out/ stopping screens), Fuller’s ability to stay with faster receivers on longer routes became compromised. Again, it’s possible that Fuller sustained an early-season/ offseason injury that accounted for the noticeable decline in efficiency from his 2019 season. But if not, then Fuller at age 29 is already falling (perhaps rapidly) out of his peak. As such, it is good that Denver signed him to a one year contract while he is likely to still be an asset on shorter routes/ the near-intermediate areas of the field.
Mike Boone (lateral oriented anterior dominant) seems to be an ideal depth RB. He is a very well rounded athlete, showing good thoracic efficiency (particularly for an RB), good lateral lumbar efficiency and no obvious red flags for injury. As a runner, he is best utilized as a ‘one-cut and go’ type back, who makes good strong initial cuts in zone runs, and runs with reasonable power afterward. However, as a pure runner, he is not particularly elusive, nor a tackle-breaker or a breakaway threat. He is a confident/ competent blocker and a solid receiver, so his well-rounded if not particularly exciting skillset can enable him to stay on the field for all three downs. And, particularly importantly for a depth player, he is an excellent special teams player, who shows good tackling, gap responsibility, and high levels of awareness. To my eyes, Boone is an ideal glue guy– he can step in and give a handful of quality snaps at RB on all three downs (particularly in a wide-zone scheme), and is a true asset on special teams. I doubt he would be able to carry a full load in the run game for more than a few games, as his lack of full efficiency in any lumbar areas would likely prevent him from being able to stay efficient over time. But as a depth RB, Boone offers plus special teams ability and good short-term running.
On a team-building level, Boone’s signing would seem to indicate one of two things (possibly both)– that the Broncos plan to feature Melvin Gordon with a true workhorse load next season, or that the #2 RB for the 2021 season is not yet on the team. To my eyes, if Boone is the #2 RB entering the season, he (unlike Lindsay before him) is no threat to Gordon’s workload, and we will likely see a carry split similar to Gordon’s split with Freeman when Lindsay was injured. In other words, to my eyes this move either signifies that the Broncos are committing to Gordon as their featured back in 2021, or that they plan to draft his complement/ replacement in the upcoming draft (or perhaps both, if the rookie is not yet up to speed in 2021).
In either case however, Boone will likely serve as well rounded/ quality depth (and a quality special teamer), capable of giving a handful of high-quality reps on all three downs, and even to carry the load (for short stints) if necessary. Above replacement level in all aspects, even if he is master of none.