Sunday, 31 March 2013

They Are(n't) Who We Thought They Were

The Canucks lost 4-0 last night to the god awful up-and-coming Edmonton Oilers, and the final score probably flattered Vancouver. This game was really over in the first five minutes when Cory Schneider regressed in a hurry, letting in two goals on the first two shots he saw. Luongo wasn't much better in relief, letting in two more on his first three shots before he settled down and made some miraculous saves that kept the score from looking really absurd. But if you want game reviews, you'll go to Canucks Army or Pass it to Bulis or something. What I want to talk about here is why this Canucks team is so painfully average.

I preface this post by pointing out that the Canucks are currently 4th in the Western Conference, and a top-10 team in the entire NHL, despite some of their perceived struggles and relentless complaining of the Vancouver market. They just rattled off six consecutive wins, and are looking like they'll make the playoffs once again. They still can be good. Ho-hum.

But they're not without their warts, as pointed out by the TEAM 1040's Jeff Paterson:
I don't really believe in excluding games from the sample, because that kind of data manipulation can be used to tell whatever story you want, but since the Nashville game is quite clearly an outlier, it's fair in this case and his point is valid - the team can't score. After last night, they sat in the dead centre of the league in even-strength goals-for per game at 15th overall, rubbing elbows with the Capitals and Wild. They're on pace for 148 even strength goals this season, which is down 12 goals from last year and 17 from 2010-2011. So, where did all the offense go? Well, let's just look at the lineup the Canucks iced yesterday:

D. Sedin - H. Sedin - A. Burrows
M. Raymond - J. Schroeder - J. Hansen
C. Higgins - A. Ebbett - S. Pinizzotto
T. Sestito - M. Lapierre - A. Gordon

D. Hamhuis - J. Garrison
A. Edler - K. Bieksa
A. Alberts - C. Tanev

The Sedins are the Sedins and we all know what they bring, even though their scoring peaks are behind them. I like Raymond and Hansen as top-6 forwards and even more as bottom-6 forwards, but Jordan Schroeder is a career 0.57 points/game player at the AHL level. Given Gabe Desjardins NHLE scoring numbers and Schroeder's production this year with the Wolves, you could reasonably expect 0.3 points/game at the NHL level, or 9 points in 30 games. Amazingly (well, not really) Schroeder has exactly 9 points in 30 games with Vancouver.

So where does that put the Canucks current #2 centre relative to the rest of the NHL? If the top-30 centres in NHL scoring are considered "1st liners," the next 30 as "2nd liners" and so on, Jordan Schroeder is a) producing at his expected level, and b) producing at an average 4th line level. As both Andrew Ebbett and Max Lapierre aren't exactly more attractive options, that leaves Vancouver with three fourth line centres. This isn't exactly conducive to firewagon, high-scoring hockey.

Unfortunately, the outlook on the wings isn't rosy either, especially in the bottom-6. Three of the four wingers on lines 3 and 4 aren't NHL players. Tom Sestito, Andrew Gordon and Steve Pinizzotto have combined for 19 seasons of professional hockey experience, but just 108 games in the NHL. While I think they've been adequate for the most part (Sestito and Gordon's Corsi's aren't awful, considering an OZone start% around 40%), great teams like the Canucks strive to be don't get to be great with half the roster just treading water.

Even though the expectations in this market are still for the Canucks to perform like an elite Stanley Cup contender, the simple fact of the matter is that the holes left in the roster by the injuries to Ryan Kesler, David Booth, Zack Kassian (who was demoted this morning) and Manny Malhotra prevent this team from being anything other than average. Other than the Malhotra situation (if they knew he couldn't play, why was he not replaced?), this is no fault of Mike Gillis or even of Alain Vigneault. You can plan for your two best play-driving forwards to be out for the beginning of the season, but you can't predict that both of them will go down with fluky injuries almost immediately upon returning to the lineup. The bottom line is that the Canucks are what they are, and what they are is an injury riddled team with three fourth lines.


Something I don't think gets mentioned quite enough outside of the more analytic circles of the Canucks blogosphere is how massive the Manny Malhotra hole is in the Canucks lineup. Since team management took Adam Smith's economic theory of division of labour to heart, every role player became of elevated importance. Suddenly, Manny Malhotra went from a guy who was good at faceoffs to a key enabler of the offense, as he allowed the Sedins to become elite 80-foot players rather than just very good 200-foot players. The Canucks effectively divided the ice up into three zones and built their team to win each individual one through situational player deployments rather than the traditional chess match of line-matching.

Not only did this get the Sedins more offensive zone time (possibly leading to a boost in true mean PDO for Vancouver like I theorized here), but Malhotra's faceoff prowess probably prevented quite a number of shots against. Some analysis done by Gabe Desjardins at Arctic Ice Hockey found that shot rates spike immediately after an offensive zone faceoff win, as shown in the below graph:

Constructed by Gabe Desjardins. Originally posted here.
Over a longer period of time shot rates converge regardless of winning or losing a faceoff, however the difference in the immediate aftermath of a faceoff is quite significant. Basically, if you have an average faceoff taker starting in your zone (like Henrik Sedin or Max Lapierre), you can expect to see the opposing team realize the dark blue line 50% of the time, and the dark green line the other 50% of the time. With Malhotra on the ice, the split becomes 40% to 60% in your favour. 

I'm not sure how large a reduction in total shots against this would lead to, but Desjardins theorized that every 245 extra faceoff wins at even strength was equivalent to two points in the standings. In the two years prior to this one, Malhotra won 70 and 118 even strength faceoffs more than what a 50% faceoff taker would be expected to win. While Malhotra's faceoff ability alone wasn't worth a win in the standings, it doesn't look insignificant either.

The opposite side of this coin is that the 2nd and 3rd line centremen currently playing on the Canucks roster, Andrew Ebbett and Jordan Schroeder, are both closer to 40% guys, albeit in a small sample. Had these two been tasked with Malhotra's faceoff duties, they would have won 135 and 208 fewer faceoffs than Malhotra did in the two seasons prior to this one, and a further 142 and 180 fewer than regular 2nd line stalwart Ryan Kesler. It's not enough to make a significant impact on the team's overall record (we are talking about faceoff ability alone here, not the other things that Kesler and Malhotra do/did do better that the call-ups), but it's one of the many little advantages the Canucks management and coaches like to have when "designing success."


The last point I'll make is how injuries have impacted the Sedins at even strength. Although they haven't been explicitly affected, they don't operate within a bubble. The state of the roster as a whole will impact how they are used and which positions they play in, and right now, the injuries to the bottom end of the roster are necessitating more defensive zone starts for the Sedins and more challenging competition.

Last year, Daniel and Henrik both started nearly 80% of their shifts in the offensive zone. So far this season, that ratio has dropped by close to 15 percentage points to 66.6% and 64.4% respectively. To their credit, their possession numbers haven't dipped at all, but along with Alex Burrows, they're seeing the toughest competition out of all Canucks forwards. The change in their deployment relative to the rest of the team is illustrated in these player usage charts. Since the charts are not on the same scale, I've added a green bubble to where I estimate the twins would be this year on last year's chart:

Player Usage Charts from Greg Sinclair's Player Usage app at
Those plush assignments AV was handing the twins? Yeah, they're not happening as much this season. This increase in QoC and decrease in OZone start% is more than likely due to Vigneault adjusting to a weaker lineup than it is any tangible change to the way the organization wants to use the Sedins. Andrew Ebbett's inability to be an average NHL faceoff guy means that the Canucks need a left-handed centre to take defensive zone draws on the left side of the ice, so by default that job falls to Henrik Sedin. Consequently, OZone start% falls.

The QoC increase is slightly more difficult to explain, but I'd guess that it's because AV really wants to shelter the AHL guys. Pinizzotto, Sestito and Gordon in particular have been playing against some of the opposition's weakest players, whereas Jordan Schroeder is seeing a lot of offensive zone starts against soft competition too. The bottom-9 of last year that ate tough assignments for the Canucks is pretty much in shambles, leaving the heavy lifting to essentially one forward line (and the goaltenders). As a result, the Sedins are seeing more power-on-power matchups this season than they have at any point in the last few years, yet they're still coming out ahead in possession. While their powerplay struggles are well-documented this year (and in my view, the only legitimate cause for concern around this team), they remain absolute upper-echelon 5-on-5 players, and should be fine in the near future.


There's the old sports adage that "injuries are never an excuse," but no one really points out that the second part of that saying should really be "for not trying your hardest." The simple fact of the matter is that while first and second liners are first and second liners for a reason, career AHL journeymen are career AHL journeymen for a reason as well. They're just not good enough to make a team effective. Vancouver is seeing this right now, as the offensive output is the lowest that it's been in years and the team has lost its chokehold on the slowly improving Northwest division. Injuries may not be an excuse, but they're a damn good reason for not winning.

The silver lining in all of this is that Jordan Schroeder, Andrew Ebbett, Steve Pinizzotto, Andrew Gordon, Tom Sestito and the newly recalled Bill Sweatt aren't in the plans going forward. Reinforcements are coming in the form of a former Selke trophy winning two-way star centre, the #1 prospect the Canucks have in their system, and if recovery goes well, an elite play-driving 2nd line winger. Management is aware of the holes that need to be filled on this roster, and will undoubtedly attempt to fill these holes this week as the trade deadline looms. This lineup isn't fundamentally flawed, the players haven't completely forgotten how to play, and Alain Vigneault is still a good coach. Now is not the time for panic, but that doesn't mean you shouldn't be concerned.

Tuesday, 26 March 2013

Lies, Damned Lies, and PDO

I'll preface this entry by saying that no, I'm not going to rail against the PDO machine. Unsustainable percentages due to randomness are a part of hockey, and regression toward the mean has been proven and demonstrated by people much smarter than myself (like the 2011-12 Minnesota Wild. Minus the "smarter" part). This purpose of this post is to address some inaccuracies I think surround PDO, as well as look at some of the concerns I have with leaning so heavily on one metric as an indicator of "luck." With that out of the way, let's get down to business.

This post was inspired in part by something Justin Bourne wondered yesterday:
Which provoked this response from one Rob Pizzola:
Well, to me at least, there are a couple of things wrong with this. The first being that while PDO may be a good indicator of team luck, it's not necessarily a good indicator of individual player luck. This is primarily because on-ice shooting% and on-ice save% are completely unrelated to one another. This should just be common sense. How a goalie performs at one end of the ice should have no bearing on how the goalie at the other end of the ice performs since they're 200 feet apart at basically all times. If you're unconvinced, I have a graph to prove it!

Relationship between team Shooting% and Save% for all teams between 2007-2008 to 2011-2012
As shown by the graph, your shooting and goaltending have nothing to do with one another. Your goalie is going to have his mean save%, and your shooters are going to shoot at some mean shooting%. On a team level, this really is irrelevant. PDO is meant to measure how much of a team's goal differential is due to random variance, rather than more demonstrably sustainable abilities like puck possession, and for the most part, others have shown it does that quite nicely.

The problem starts when PDO is used to explain individual output, like the Pizzola quote above. Comparing Seguin's stat lines over his young career, you'll quickly see why his PDO this season is so high:

Top row is 2013, bottom row is rookie season in 2010-2011
What Seguin's benefiting from this year is an unusually high on-ice save%. Now, Tuukka Rask sports an impressive .927 at evens for his career (that's Roberto Luongo territory), so a higher on-ice save% than normal should be expected. Compared to last year, Seguin's higher PDO is being driven by a factor he has basically no control over.

So this season, he's experiencing a boost in Corsi, a higher on-ice shooting%, an elevated PDO, but a decline in production from 2.69 EV pts/60 last year to 2.26 EV pts/60 this season. Just from looking at PDO, Seguin should be having good luck, and instead his actual even-strength output is down across the board. PDO does not capture why, nor does it show that he's actually getting lucky in the offensive end of the ice. Therefore, it cannot be concluded that his production will change either way based solely on a high PDO.

(Since the purpose of this post is to demonstrate that PDO as it is frequently used doesn't always capture good and bad luck on an individual player level, exactly why Seguin's production is down isn't really relevant to this discussion. I suspect though that it's because his individual shooting% is below what his true talent mean could be. Behind the Net shows that he's shooting below 6% this year, compared to the 8.3% he shot last year. Of course, there's also the possibility that he's David Booth 2.0. Also note his frequent linemate Brad Marchand shooting near 14% in each of the last two years. That's probably the source of the high on-ice shooting% number Seguin's PDO has enjoyed.)

The second real problem I have with PDO on an individual level is the idea that all players will have an individual mean PDO of 1.000 and any deviation from that is due to variance. We already know that on-ice shooting% and save% are unrelated, so let's ignore the part of PDO that a player can't control and assume that on-ice save% will regress towards your goalie's true-talent mean save%. This leaves a player's on-ice shooting% as the aspect of PDO a player can control to some degree.

If I remember what I read a while ago, Gabe Desjardins argued that there was no such thing as discernible shooting skill, and all offensive output was the result of either puck possession, luck, or a combination thereof. Someone else (I want to say it was David Johnson of, but I'm really not sure and I don't want to put words in anyone's mouth) disagreed, arguing that elite players demonstrate consistently superior shooting abilities. I tend to agree with this dissenting opinion, largely because I live in a market that sees David Booth play more frequently than anyone else and holy hell that man can't shoot the puck in the net. As a result, I have a tough time believing that there is no difference in skill between him, a 4th line crash-and-banger, and say, career 17.3% shooter Steven Stamkos or career 15% shooter Sidney Crosby.

In fact, this discrepancy between "talented" and "stone-handed" forwards is illustrated quite nicely in some analysis Tyler Dellow posted this morning as I was writing the first part of this up. Also looking at stuff inspired by Justin Bourne (basing the good player/bad player distinction on Corsi), he posted this table:
Courtesy of Tyler Dellow at Go read his things and laugh at his beloved Oilers plight.
The biggest thing I took from this table is that the shooting% of first liners do exceed that of fourth liners by quite a significant margin (note: it looks like Tom Awad found this distinction too, as Eric Tulsky pointed out in the comments of Dellow's analysis). For the purposes of this argument, let's make the assumption that the average individual mean on-ice shooting% for each first line player is 9.22%, and the average individual mean on-ice shooting% for each fourth liner is 6.24% as Dellow found in his analysis. This means that for a Boston Bruin first liner like Tyler Seguin, they can reasonably expect a mean PDO of 9.22% + Tuukka Rask's 92.7% save%, for an expected individual PDO of roughly 1.02, which is nearly exactly what his PDO was last season. By comparison, a Bruins fourth liner can expect a PDO of around 0.989 with the difference being attributed to finishing skill.

As this is the case, 1.000+ PDOs for first line forwards are not due simply to good luck. Similarly, sub-1.000 PDOs for third and fourth line players are not necessarily due to poor luck either. A player with a PDO of exactly 1.000 - which we consider to be operating at exactly at his expected output with no good or bad bounces - may actually be experiencing a fair amount of variance and can still regress to his individual mean either way, depending on their talent.

So, from all this stuff, there are two main takeaways:
1) PDO does not capture luck on an individual skater level.
2) The mean that PDO can be expected to regress to is unique to each player, and is influenced mainly by that players role and shooting ability.

With these points in mind, I don't think using PDO to make judgments on an individual player's point production is particularly wise. It's a relatively small and seemingly obvious distinction to make, but still an important one nonetheless. It's why I tweeted this to Justin Bourne yesterday:
PDO is good for the broad-brush analysis on a macro-scale ("the Ducks' record is unsustainable!"), but it's "predictive" power doesn't really carry over to a micro-scale, because you're not dealing with nice, round numbers anymore and PDO's two components are completely unrelated to each other. Regression will always happen, but it's not as cut-and-dry as the familiar "it will regress to 1.000!" mantra, at least not on an individual level.


As as aside from the above discussion, something Thomas Drance wrote today got me thinking. Mostly, it was this quote:
But that capital is evaporating as quickly as Vancouver's strangehold on the Northwest Division. Part of the reason that the court of public opinion has slowly begun to turn against Mike Gillis is, in part, that for the first season since 2008-09 Vancouver's PDO (PDO is the sum of a team's shooting percentage and save percentage, and functions as a shorthand measurement of puck luck) isn't two standard deviations above the mean
Emphasis is mine. Basically, and this is idle speculation on my part, why can't Vancouver maintain an elevated PDO? On the surface, this is a dumb question, since the answer is "regression." But, as Tyler Dellow and Tom Awad have found, more skilled players have the ability to maintain higher on-ice shooting%, and in Vancouver, Alain Vigneault has done nothing but feed the Sedin twins offensive zone starts over the past three seasons. In fact, both Dellow and Awad identify Daniel Sedin as one of the few players in the NHL that has elite puck possession and finishing skills.

With the Sedins seeing the lions share of Vancouver's offensive zone starts, it means that the Canucks will see a higher proportion of their shots on goal taken by 9%-10% shooters than other teams do. Of course, this also means less offensive zone time for the below average finishers on their roster. This would mean, just from a simple weighted average, the Canucks and Alain Vigneault can effectively inflate their team shooting% above what it would normally be under more traditional player deployments (I also think AV is the main driver behind the Sedin's strong Corsis, but that's a topic for another day). This, coupled with elite even strength goaltending provided by Roberto Luongo the past few years, would lead to a higher than 1.000 mean PDO.

Of course, this could mean that the "elavated" 1.011 PDO Vancouver is operating at so far may in fact be below the Canucks' actual mean, and there could be room to regress upwards. It's an exciting thought for a Canucks fan, and an interesting one too, especially considering the recent (and favourite of Thomas Drance) quote Lawrence Gilman gave Elliotte Friedman:
But believe me when I tell you there are percentage results that allow you to coach and manage your team to hedge bets in certain events.
Could this PDO manipulation through player deployment be the influencing of "percentage results" that Gilman's talking about here? It's possible, but the Canucks are understandably coy about their analytic black box. That's not going to change anytime soon, either. I mean, these aren't the Toronto Raptors we're talking about.


One more thing, I still think PDO should stand for "Percentage-Driven Output." Give it a real fancystat name already.