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Boston Bruins Midterm Grades - Defense

How's the revolving door of Bruins defense getting the job done halfway through the season? We'll compare what we should expect from their usage to the reality of what they've delivered to see who makes the grade.

We've had some weather related delays
We've had some weather related delays
Mark L. Baer-USA TODAY Sports

I know we're a little late for midterms. Look, we had some snow storms and had to make up the exam, ok? So at 8 games past the mid-way marker, lets take a gander at our squad and see who has made the grade through the first half (plus).

Over the past couple seasons, our writers have applied various metrics to their grades in an effort to make these rankings less subjective, using things from CorsiRel to Goals Versus Salary. In an attempt to gauge defensive contributions, this year I'll be taking a page from Pension Plan Puppets' Stephen Burtch (@SteveBurtch), applying what he developed as Shut Down Index and fellow PPPer Andy Dabbikeh (@Frag_IDMA) expanded on and perhaps more descriptively named as deltaCorsi, to evaluate how much impact the Bruins defensemen are having at keeping shots against down, as well as generating them for, in contrast to what we should be expecting from them given their usage.

In brief, the concept of what we're doing is pretty simple, even if the math behind it might seem a little unapproachable. We'll be doing as we typically do, evaluating a player's performance while taking into consideration the context of the situations he plays in. We're just going to be doing it without sifting through at a host of different metrics - deltaCorsi combines them for us by accounting for how much Quality of Teammates, Quality of Competition and Zone Starts impact shots against and for. Weighting each by the correlation coefficients found from league-wide analyses of each input value's relation to shot attempts, we derive what we should expect from the average player facing  any usage condition. The "expected Corsi" figure that results is then compared to the actual performance to give you their "delta Corsi," or the positive or negative difference from average expected results. How much above or below average given their specific deployment, which is perfect for our intra-team grading purposes.

(If this sounds like voodoo to you and you'd like to get into the nitty gritty of the new combo-stat's statistical significance and a more detailed explanation of the process, I highly recommend you read up on Steve and Andy's posts on the subject and for supplementary reading Pierce Cunneen's (@pcunneen19) study on the impact of Quality of Teammates vs Quality of Competition, which elaborates on how one value carries more weight over another.)

The below table shows Corsi Against and For per 20 minutes, the expected values of both /20 given their usage and then the difference between the two, delta Corsi, also /20. To look at the input values of QoT, QoC and Zone Starts, please feel free to peruse this spreadsheet. Data is culled from

Player CA CF exCA exCF dCA dCF dCorsi
Zdeno Chara 16.396 20.442 17.903 19.787 1.507 0.655 2.163
Johnny Boychuk 16.514 19.949 17.789 19.712 1.275 0.237 1.512
Dougie Hamilton 16.547 19.280 17.437 20.188 0.890 -0.908 -0.018
Torey Krug 17.299 21.021 15.961 20.746 -1.338 0.275 -1.063
Adam McQuaid 17.199 17.346 17.671 20.025 0.472 -2.679 -2.207
Matt Bartkowski 18.071 18.337 17.193 19.675 -0.878 -1.338 -2.216
Dennis Seidenberg 19.043 18.913 16.572 19.916 -2.471 -1.002 -3.474
Kevan Miller 16.553 16.159 16.516 21.379 -0.037 -5.221 -5.258

Now on to the grades

Zdeno Chara:

So, this franchise defenseman is pretty good at defense...


What? Crazy! Who knew!? While his deltaCF is solidly above half an event per period he's suppressing over 1.5 compared to the rest of his team - which already posts really good numbers in this regard. All this while facing the league's best players from the defensive zone up. The guy with the hardest assignment still yields the best CA of the bunch. Yeah, he's good. As you'd see if you click over to Frag's spreadsheet of six-year numbers, Z's been doing this for a while too. He's far and away the most impactful defenseman in the fancystat era, with only Subban and Webber entering the same solar system.


Johnny Boychuk

Trailing behind Chara this season is his sometimes partner. But while your initial reaction may be "well yeah, he plays with Chara," keep in mind this metric accounts for the impact of the extremely high QoT implicit in playing with Z and Bergeron a whole lot, and Johnny still outperforms lofty expectations. Not to mention that thanks to the roster volatility on the back end, he's actually spent more time rotating through the pairings than playing with Z. This is borne out in Boychuk's WOWY chart, if you'd like another view - he gets some drop in CA when he departs his customary duo, but gets an uptick in CF. At this point, it looks like he could legitimately anchor a second pair himself. Our Johnny's growing up!


Dougie Hamilton

Unlike his rookie season, wherein his impressive dCorsi was the product of exceptional o-zone territorial advantage and decently solid d, he's dropped off considerably in the former and improved notably in the latter. He's fallen below expectation overall, albeit by a factor so minute it amounts to a net 4.5 shots attempts against all season. So you could basically say he's right at par. And he is encouragingly contributing close to a full shot/20 of prevention. Perception that he's rounding out his defensive game appears to be accurate, but one has to question where his contributions at the other end went when his deployment hasn't really moved an inch.


Torey Krug

The Bruins leading scorer on the blueline, challenging for team rookie records is ranked fourth on the current crew and doesn't merit a stellar grade?


(Dallas Eakins is SHOCKED!)

Would it at all surprise you to hear that the positive input value in Krug's rating is entirely by virtue of offense? Given his pretty extreme sheltering, we should anticipate pucks being wailed unremittingly at the opposing goal with him on the ice, and lo and behold, he exceeds even those lofty expectations, if modestly. So he's real good at that bit. Meanwhile... Given the lightweight QoC, damn fine teammates (largely at forward, admittedly) and rarity with which he sees the d zone, he should be seeing nearly league lows in shot attempts against. He falls quite short, landing in territory below Boychuk's zone-burried, top competition expectations. That is not great. He lands second-to-last on team in dCA and third worst in raw numbers while having the most favorable starts of anyone. Since we're only considering even strength, lets bump him half a grade for doing damage on the powerplay, where he's developing into something of a specialist. 5v5? Not all that special. Break in case of man advantage and continue sheltering the hell out of him.

C (subjectively adjusted to C+ due to special teams)

Adam McQuaid

Even accounting for the fact that he's being entrusted with more defensive zone duty than prior years McQuaid's offensive impact is horrid. His meager yet career year rivaling production is based on a team high PDO. But who expects offense from ol Punchy-face? On the defensive side, he's having a slight but not insignificant suppressive impact this season. In other words, faced with easy but not quite the easiest usage he's a little better than average. For defense-only purposes, he's probably the best option for the third pair at this moment out of the choices on the table.


Matt Bartkowski

Fourth-year pro Bartkowski on the other hand doesn't really do anything all that well. Given his notable ability to skate the puck out of the zone one would think he'd have a correspondingly positive impact on the team's offense, but he delivers third worst on team ahead of only McQuaid and Miller. On D he more or less has the same expectations as Hamilton and goes in the opposite direction. The balance of below-average sub-mediocrity on both sides of his dCorsi land him in a statistical tie with McQuaid, but the latter looks to be the safer option if forced to choose between the two thanks to his stability on the back end.


Dennis Seidenberg

Most consider Seidenberg's injury a major blow to the blue line. But might the team actually be better off without Der Hammer?


Dennis Seidenberg runs away with absolute worst dCA on the team, single-handedly erasing the gains made by Chara's out-performance. His closest comp league wide? Robyn Regehr... Given Seidenberg's gradual move to the middle of the pack in zone starts and QoC this season with Z and Boychuk taking over the toughs, we really should be witnessing some improvement, but he's instead throwing up a team worst CA rate. Like a bizarro Chara, Seidenberg has been vastly underperforming for several seasons. To sum it up, with Seidenberg on the ice we're facing more rubber than anyone else by a long shot, and there's no facet of his usage that should explain this away. Is there some other explanation for his much heralded defense? Well, there is a one foot average shot-against distance discrepancy between his On and Off numbers, but that pushing shots that small distance is hardly going to move the needle. I'd wager it's more because that's where we see him most, hustling so damn hard to keep the puck out of the net because it's always headed that way. Sure, he's damn good at blocking shots. He gets a lot of practice.


Kevan Miller

I'll say straight away that Miller gets a bit of a raw deal by this measuring stick as a result of the inequitable samples involved. Given the vast amount of time his teammates and opposition have spent away from him and the performances they've thrown up without him, coupled with laughably low QoC, he's anticipated to have extremely high CF. Obviously he's going to fall short - but that said he delivers closer to a figure befitting the Toronto Maple Leafs. His expected CA is likewise a bit artificially low, though not all that unattainable. Here, he almost hits the low bar exactly. He's literally replacement level on D. Looking just at his CorsiON he's still in the black, though he's performing below the level of Bart and McQuaid in spite of much easier deployment. I welcome his signing as a depth option, though I'm skeptical of his ability to render even McQuaid irrelevant. I'll spare him a failing grade for doing no harm on the D side.



While acknowledging that we're down one in Seidenberg's minute munching absence, his injury could turn out to be a boon for the team based on the impacts we see above - if and only if his replacement isn't cut from the same cloth. Now that we've a picture of the existing D, graded on a bit of a curve within the team, lets take a gander a couple guys who have been brought up in conversation for trade relief form Seidenberg's extended vacation.

We can make a couple assumptions based on dCorsi from around the league. First, with QoT being the biggest outside factor influencing a player's possession numbers, it's reasonable to assume that a rise in this facet by moving to a better team will result in better numbers. Looking for guys who vastly outperform their teams with bad QoT is a good way to find diamonds in the rough when raw counting or fancy stats might not obviously jump off the page. Secondly, moving aplayer under tough usage to an easier deployment scheme should provide similar results. In short, we're mining bad teams for the guys that acquit themselves in their dreadful cohorts' toughest minutes.

The table below is a mix of oft-mentioned names and personally desired targets after delving into this statistic.

Player CA CF exCA exCF dCA dCF dCorsi
Christian Ehrhoff 19.528 16.530 21.138 14.739 1.608 1.791 3.398
Mark Fayne 13.180 16.326 14.277 16.192 1.097 0.134 1.231
Tom Gilbert 17.075 18.788 17.264 17.375 0.188 1.413 1.602
Dan Girardi 18.601 18.807 17.993 19.746 -0.608 -0.939 -1.548
Ron Hainsey 17.342 18.652 21.669 19.447 4.327 -0.795 3.532

Christian Ehrhoff, BUF

Saddled with a dreadful team in his third full season in Buffalo, Ehrhoff exceeding expectations shouldn't really come as that much of a shock. But think of his performance like Jagr practicing with his weight vest: he's gotta work that much harder to carry all that dead weight around the ice. And it just so happens Seidenberg's putting up the same CA rate without the vest. Ehrhoff's raw numbers aren't going to make anyone jump to acquire him but he won't be thrown to the wolves competition-wise were he to come to Boston, and his QoT would see a major jump even playing with the team's THIRD tier of talent. My god Buffalo blows. Saving the pros and cons of his cheap but long contract for another day, Ehrhoff would be a clear upgrade for the second pair. And he would maintain the team's German quota.

Mark Fayne, NJD

Among all D with over 500 minutes this season, Fayne leads the league with the lowest CA/20. And as his expectedCA shows, this is good even for his second-best-in-league team. Playing for a low-event Devils squad where Corsi Against is exceedingly depressed as a team, the fact that he blows away even these expectations should raise eyebrows. A look at his career deltaCorsi in NJ offers similarly enticing results. Like Hainsey below, he's not seen top-pair minutes, and his WOWY indicates that this season unlike prior he benefits to some degree from Andy Greene's performance. Even so, for a pending UFA often scratched by DeBoer for less than capable replacements, this might be a situation ripe for exploiting another organization's inefficiency.

Tom Gilbert, FLA

Perhaps one of the best cheap pickups all summer, Gilbert sat on the market for months before signing a PTO in the land of second chances, Sunrise, Florida. The Panthers took a no-risk shot in the dark at a guy who couldn't find a job to save his life, signing him to a one year, 900k deal that saw him blossom into a productive top-minute D. Though Florida has dropped to a 1.6% shot at the playoffs, it remains to be seen if they'd be willing to part with their inexpensive find, though given his age he can't possibly be in their long term plans and he'll never have more value as a tradable asset. His exCA,which he's marginally exceeding, would translate directly to the Bruins second pair and a move to a more offensively capable team should see a bump in his production. Seems like he'd be a plug and play option for the available slot in question. (Sticktap to Gus for this pick)

Dan Girardi, NYR

Coming from a possession team within spitting distance of our own, Girardi's expected values compare pretty directly to those on our own tough-deployment gang, so don't assume a huge bump based on QoT - in fact, placing him on a lower pair could continue his habitual underperformance. Faced with numbers matching those of Boychuk, he basically gets the opposite results, falling a net 1.5/20 below. That's not to say that he wouldn't be a functional replacement as a second pair defenseman, but he's not cutting it in top pair minutes and isn't a shoe-in to improve under Seidenberg's usage. He'll be owing his coming UFA deal largely to his partner McDonough. Move along, nothing to see here.

Ron Hainsey, CAR

At first blush, it looks like Hainsey makes an enormous difference to his team keeping shots down per his dCA and would provide the same for the Bruins. However, there are a few asterisks alongside him. First, his QoT is surprisingly high and not an epic gulf from the B's 2nd pair ala Ehrhoff and Gilbert. Also, Hainsey is already being rolled out as a 2nd pair guy, so his performance doesn't look like a lock for improvement due to being placed in an easier role. Seems as though he might be a bit more of a gamble, though should offer an upgrade to what was there before.