With the signing of Desmond Bishop, the Minnesota Vikings have shored up a position of weakness as they reload for the 2013 season.

Fresh off of a 10-6 record and a playoff berth, a repeat performance from the Vikings will require sustained improvement in key areas; if you're not getting better, you're getting worse.

With the departure of Jasper Brinkley (addition by subtraction, perhaps), the Vikings have found themselves with a big hole at middle linebacker—or at the weakside position depending on how Erin Henderson fares at middle linebacker.

The former Packer was an inside linebacker in their 3-4 system, but was previously drafted as a linebacker in their 4-3 system—the backup MLB in 2008, in fact. He played as a middle linebacker in Bob Gregory's 4-3 defense, and they were forced to switch to a 3-4 shortly after Bishop left.

He told NFL AM that he played in a 4-3 defense in high school and earlier, so the scheme switch shouldn't be too difficult.

But the Vikings' 4-3 system is far different than Gregory's or most high schools and it certainly wasn't the same as the Packers' 4-3 under Bob Sanders.

In the Packers' system, Desmond Bishop was called the "Mack" linebacker, often described as the weakside inside linebacker for Dom Capers' 4-3 system. There are any number of descriptions of the Mack and Buck linebackers floating around, some specific to the Capers system, and they may help illuminate his fit in the Vikings' defense.

A detailed Packers blog titled "Where's Lambeau" likened the Mack linebacker to the Will position, avoiding blocks, navigating traffic and making plays. The same is true of Steelers' Depot, who use the same words to describe the Buck and Mack positions as others have of the Sam and Will positions on the defense.

The SBNation website for the Steelers agrees, further adding that the Buck typically calls the plays while the Mack may not even have an assigned gap.

Article after article listed Bishop as the Mack linebacker and Hawk as the Buck linebacker, but the three games I tracked found Bishop lining up over the strong side of the formation much, much more than those designations would imply. There's even a good chance that he lined up on the strong side more often than Hawk.

At any rate, it looked like Bishop was just as involved with defensive calls and team leadership, if not moreso, than Hawk.

I chose to highlight games that Pro Football Focus identified as his best, worst or most representative game. In this case, I also chose high-leverage games, where the results were more important than usual. Because of that, I chose his game against the New York Giants in the divisional round of the playoffs, a Week 16 game against the Chicago Bears (if they had lost this and the next game, the Saints would've grabbed the first seed) and the Week 2 game against the Carolina Panthers, because I wanted to see him take on a mobile quarterback.

Coverage

In these games, he would line up in the middle hook/curl zones the most often, or line up against a tight end—Jake Ballard, Kellen Davis and Jeremy Shockey, in this case. None of those tight ends are amazingly athletic, but they approach the game in a few different ways that are good to test a linebacker like Bishop with.

He also therefore played against a variety of running schemes. Cam Newton had designed runs as well as option plays, New York runs a flexible zone scheme and the Bears ran a power blocking scheme (under Trestman, they will switch to much more zone blocking, incidentally).

Over those three games, Bishop dropped into coverage 95 times by my count and 106 times by Pro Football Focus. I'm pretty sure some of the discrepancy comes from grading "green dog" calls, where the linebacker is assigned man coverage against a player unless that player stays in to block—in which case, the linebacker blitzes.

Of those 95 coverage snaps, I saw 14 targets (PFF has 16—they included tunnel screens on man coverage and I did not) and I saw "12" completions. I counted passes where the receiver should have caught the ball but didn't while PFF did not, and they recorded 10 completions.

10 of his targets came in zone coverage (65 of his coverage snaps) while 4 came in man coverage (30 of his coverage snaps). Because context goes into the defensive playcall and also determine who the offense should be first in a progression, I don't read this as "Bishop is better in zone coverage" by default, although I'll get to that later on.

This all fits the general coverage patterns that Bishop has had. He ranked rather low among linebackers during the 2011 season, with a target coming in his direction once every 7.2 snaps. The average inside linebacker had one come every 8.33 snaps.

More worrisome, Bishop allowed 1.38 yards per snap in coverage, which was the third-worst mark for a middle linebacker in 2011. The average player at his position allowed 0.92. This staggering difference implies some serious problems with his coverage.

From what I saw, Bishop is never way off his target, merely off enough to allow a starting quarterback to find his target. A good example is below, where he plays the middle-most linebacker and plays man technique, trailing a bit too much and too early to reasonably expect the safety help that should be there soon.





He gets beaten by a fairly simple move at the stem and doesn't quite recover. It's a relatively common feat, although the windows he leaves open are usually tight anyway. Sometimes, he plays perfect coverage.

Here, he picks up the man entering his zone without biting on play-action (or rather, he remains cautious about the run), allows a seamless transition for that receiver to enter another zone, and then rolls his coverage according to the conditions on the field (which include a QB that has picked what side of the field he'll read). He nearly gets the pick by adjusting to the throw and accelerating tot he catch point.

These examples are few and far between, however. One of Bishop's weaknesses is a propensity to bite on play-action passes and miss out on getting appropriate depth in coverage. He doesn't have quite the agility to recover from those mistakes most of the time, and so will be caught out of position.

Bishop also rarely backpedals as well as he does in the above GIF, often relying on bailing to get to his depth marker, which is not often a too demanding responsibility. Of his 65 zone coverage snaps, I found that Bishop was asked to defend the Hook/Curl zone 54 times. His responsibilities were rarely to defend deep and most of his deep responsibilities (of which I counted six snaps of) were in relatively special situations, like 3rd and 17.

Generally speaking, I found Bishop to have some qualities you really want in a zone coverage defender: a quick click-and-close instinct (two of the three pass deflections I recorded were the result of him closing in on the receiver faster than the QB expected) and he does a decent job reading the quarterback to anticipate the throw.

At other times, he had a lot of work to do. Bishop will sometimes display the awareness to roll the zones in response to what's happening on the field, but too often remains static once he hits his landmark. Pro Football Focus went into great detail on what it means to shift zone coverage based on field context, and why it separates average players from good players (and sometimes good players from great players).

Zone schemes require more mental faculty, because players don't simply need to process one or two people or keys as they play in coverage; they need to constantly shift their actions as a result of field conditions. Most players even in the NFL don't do that, and unfortunately, Bishop isn't an exception.

In general, Bishop understands his assignment, but doesn't change it to suit conditions. This leads to too many reception opportunities for opposing offenses and is part of the reason why he gives up so many yards without being asked to defend deep zones.

As a man coverage player, he exceeds his athletic talent (which is above average for an NFL linebacker, but not eye-popping) and has a solid ability to stick to his assignment. Unfortunately, like the GIF above illustrates, he will often still be a step behind and present a passing window to opposing quarterbacks, but it is not a terrible window to give up.

The biggest issue is that his recovery speed is slow and therefore can't afford to make too many mistakes. His savvy is excellent and aside from play-action problems, he rarely makes mistakes in man coverage because of deception by the receiver. It just so happens that when he does, it leads to bigger gains. He doesn't have great top-end speed and will be taken advantage of by speedier tight ends.

What I do like is that he's smart and studied enough to continuously play matchup-zones, which require a high degree of film study, intelligence and a good understanding of offenses and route patterns. It gives him a leg up and allows him to mask his weaknesses as both a man coverage defender (in that he doesn't have to pursue receivers outside his zone and expose his poor long speed) and zone coverage defender (requiring more focus, but less zone flexibility).

Bishop is extremely physical in coverage and is well aware of the 5-yard restrictions on when he can or cannot bump a receiver. Nevertheless, he continuously imposes himself physically on a potential receiver throughout the route in man coverage and hits hard in zone coverage when the ball gets to its target.

Sometimes, he has to match up with a slot receiver and the results can be fairly comical. In the GIF below, look at the bottom linebacker (the defensive player second from the bottom lined up over a receiver):





Overall, this bore out to a worrisome 119.9 passer rating allowed in 2011. The good news is that "passer rating allowed" does not really repeat itself a lot from year to year. The bad news is that the amount of yards per snap in coverage is much, much more likely to repeat.

Run Defense

Desmond Bishop shines as a run defender. I was trying to figure out if there was a way to pin down a better statistic for determining instincts, and I came up with "tackle opportunity per snap": adding tackles, assists and missed tackles in the run game and dividing them by the number of run snaps taken.

It doesn't paint a complete picture, but aligning it with run stops as a percentage of total run tackles (where "stops" are defined as a "loss" for the offense—tackle for loss or for minimal gain) would help illuminate the picture.

In 2010 and 2011, Desmond Bishop led the league in tackle opportunities per snap, with a combined TOPS of over 25 percent.

That's not just of all inside linebackers, that's of every player.

The average for inside linebackers is just below 19 percent. This means he got to the ballcarrier in the run game more often than any other player in the league, and by a significant margin (nearly 25 percent more often than the average linebacker).

Constructing a tackle map of where he made those tackles underscores the point, but what brings it home is which percentage of run snaps ended in "stops". Of all inside linebackers who competed in both 2010 and 2011, Bishop ranked 10th, meaning he had more tackles that made a big impact than a significant portion of the league, with about 10 percent of his run snaps ending with him stymieing the offensive run game.

Not only that, he rarely misses tackles. Once again combining 2010 and 2011 run performance, Bishop grades out as the fourth-most efficient inside linebacker, only missing a tackle once every 16 tackle attempts.

All of these statistics match up well to a lot of what I saw on film, although his Chicago game left a lot to be desired.

Bishop possesses excellent run diagnosis and often has a jump on the direction or flow of the player faster than the rest of the defensive players, and consistently has a talent to be in the right place at the right time. Patrick Willis, arguably the game's best middle linebacker right now, emphasized how critical that is when he said that playing smarter is simply better than playing fast. It's why Ray Lewis stayed relevant.

The former Packer has that instinct in the run, and he rarely sacrifices gap responsibility in order to get to the runner.

When approached by blockers, he'll often have the ability to loop around, get skinny, or otherwise shed them. On occasion, if the offense has tipped its hand, Bishop will knife through the offensive line to make an impact play.





In the above GIF, he attacks the "C" gap, bounces out and releases from a tight end in order to make the tackle in the alley. When he targets his blockers like a Will linebacker—using half their body as an aiming point—he does a good job of getting skinny or elusive and avoiding the block. On the other hand, when he's caught (or actually has to "stack" and take on the lead blocker to free up others), he's more likely to get pushed out of the play.

It's not that he can't hold his position when put up against a lead blocker, it's simply that he sometimes sets incorrectly and plays on skates, or gets blocked from the side. I don't think he'd necessarily be a bad Sam linebacker, but he's clearly better when he's asked to navigate traffic, not clear it.

His tackling technique could use some work. He doesn't have the consistency of Greenway or Henderson, but so far his results have been pretty good. He has strong hands and can use those to his advantage. More than anything, his instinct to get low on his tackles allows him to deliver both power and generally hold on has helped him maintain his good tackle total.

Here's a good example of how he can shed a blocker or two to get to the ball carrier and establishes a base from which to tackle. In the GIF below, he is the linebacker in the middle of the defensive formation, lined up on top of the bottom hash (wearing white sleeves):





It should be said that Bishop was selected as Pro Bowl alternate, but his 2011 resume likely didn't warrant it. In 2010, however, PFF ranked him as the 5th best inside linebacker.

There's a lot of validity to a ranking like that, and a player who can consistently make an impact against the run on an every-play basis warrants consideration.

EDIT: I've constructed a hasty tackle map based on those three games. Below, you can see a tackle map, where the dotted line is the down marker. Mondo said it would be a good idea, so here it is.





On the map, X's are "good tackles" that constitute a tackle in a good place to bring down the ballcarrier. O's are either missed tackles or times when the linebacker was blown out of position by a blocker when he shouldn't have been (when stacking, for example). Triangles are tackles made when it is in a bad place to bring down the ballcarrier. It is important to note that those are still good plays—90% of the time, he is making up for poor team play, not making a bad play himself. This is for those three games and do not include sacks, but do include scrambles.

Miscellany

In addition to how he plays in coverage or how he plays in run support, Desmond Bishop is an effective and accomplished blitzer, often beating guards or centers to put pressure on the quarterback (sometimes beating tackles and tight ends). In 2010, Bishop was the second-best inside linebacker at blitzing, according to Pro Football Focus' Pass Rusher Productivity rating, which measures not just sacks, but hits and pressures—then weights them and divides by pass-rushing snap counts. The gap between him and first (Patrick Willis) was small, but the gap between second and third was enormous—Bishop was 25 percent more effective than third place Kevin Burnett.

In 2011, he was less effective (placing 11th), but still recorded 5 sacks, the second-most of any inside linebacker.

The Vikings didn't blitz very much (Jasper Brinkley had the second-fewest pass-rushing snaps as a percentage of his passing downs of any inside linebackers), so in order to take full advantage of this, they would have to change their defensive philosophies. Given the adaptability that Alan Williams has shown as a defensive coordinator, it's entirely possible that the Vikings would deploy more blitzes, especially because Jared Allen is a talented zone coverage player (for a defensive end) and Everson Griffen has significant experience in zone coverage as well.

Beyond that, the Vikings have a secondary well-suited for press-man coverage and would take advantage of the complementary talents of its defense with the classic blitz approaches as well.

He's a smart player that clearly took a leadership role on the field, which isn't in short supply for the Vikings but is still nice to have. Should he earn a starting spot with the Vikings, its clear that he'll assert his experience in the form of authority and will consistently make sure that players follow through on assignments.

Role

Honestly, I don't see Desmond Bishop as too different a prototype than Erin Henderson, although Henderson is better at stacking blockers. Henderson doesn't have the same statistical output that puts him near the ballcarrier, but does demonstrate the same base skill of reading and reacting to the run play.

The statistical measure, which I've called TOPS up ahead, is biased in favor of 3-4 inside linebackers (although, Bishop's dominance in TOPS far exceeds the bias), but even after correcting for the bias, Henderson is not as good. As the fourth-best outside linebacker over the last two years in this metric, he's no slouch—almost elite at getting to the runner—but Bishop has been the best.

As a coverage player, Henderson has not been tested in high-leverage situations nearly as often because of his role as a two-down linebacker, but his limited exposure has been much better than Bishop's. Not that it's good. Henderson ranked as the 11th-worst outside linebacker in yards allowed per snap in coverage, while Bishop placed as the third-worst inside linebacker in 2011 in the same metric. Henderson has much more experience dropping deep, but he also has agility and speed problems.

Bishop has a better pure backpedal, but Henderson is better fit to drop deep. Given that outside linebackers are targeted more often, it's not quite fair to compare how many targets they incur per snap (and much of this is determined by the skill of other coverage players), but Henderson's numbers in 2012 were significantly poor—almost as bad as Bishop's. The difference is that Henderson was very good in coverage in 2011 and ranked 7th in cover snaps per target out of outside linebackers, and was 6th-best.

The discrepancy in his coverage statistics imply that Henderson has much more untapped talent than someone who puts up consistently poor numbers like Bishop. On film, Henderson seems to have a better understanding of how zone coverage needs to adapt to receivers and quarterbacks, and also is much more fluid in man coverage or matchup-zone situations.

As a result, I would feel more comfortable putting Bishop in as a Will linebacker who is largely focused on stopping the run and avoiding blocks. Henderson has comparative advantages in skills more closely related to Tampa-2 Mike responsibilities, and has the added benefit of being much better against play-action; a more deadly fault for a deep coverage player.

Given that the Mike is much more likely to take on blocks, it also makes sense that putting Henderson in at the Mike would also maximize the team's talents.

Still, their talents are far closer in style and depth than some of the smaller differences I've pointed out seem to emphasize and either could be better suited to each spot given camp performances. Both have big holes in their game but are also excellent at skills that fit either linebacker position. There should be no question that the addition of Desmond Bishop clearly upgrades the Vikings' linebacker situation.

The development of Mauti and Hodges—who displayed far different skill sets in college—definitely adds talent and variety to the competition at linebacker, and it shouldn't be too surprising if one of them walks away with a starting position, either. At the same time, both have obstacles to overcome and might need to wait out a year.

Nevertheless, adding talent to what was once a weakness, is an important step to turning the linebacker corps into a strength. It's not quite there yet, but it might not be far from it, either.