Thursday, June 25, 2015

Why History Suggests Carey Price Deserved the Hart Trophy

I'm generally a fan of the Washington Post's Neil Greenberg, but in the wake of Carey Price sweeping the NHL awards last night I feel obligated to respond to an argument that he has championed this season.  It's been expressed in a few different ways (and by other people as well, of course), but generally has come down to some version of the claim that since goalies have rarely won the Hart Trophy historically, Alex Ovechkin should have been the expected and possibly more deserving Hart winner.

To quote Greenberg from yesterday:
"But would the voters name Price as the league's most valuable player over Ovechkin?  History shows they haven't in the past."
Obviously the voters did overwhelmingly name Price as the league's MVP (and so did the players).  But Greenberg was not so much predicting the result as making a claim from historical evidence, which means that it is not the presence of hindsight that allows me to challenge his assertion.  I'm not interested in criticizing anybody because their guy didn't win, but I am quite interested in what history says about the relative comparison of forwards vs. goalies, since that is an interesting problem of player valuation.  My contention is that history actually shows that the voters were completely consistent in backing Price, and would in fact have been just as likely in years past to choose a goalie season equivalent to Price's over a scoring season like Ovechkin's.

Wednesday, April 22, 2015

Are Swedish Goalies Overvalued?

In doing the research for my post on Jacob Markstrom, one of the things I did was run the numbers for all Swedish goalies who have played in the NHL over the past 25 years.  That chart didn't end up making the final cut, but it was interesting enough on its own that I want to post it in here in the context of a discussion on the recent performance of Swedish goalies in the NHL and what that might be able to tell us about the effectiveness of that country's goalie development model.

Here is the complete NHL performance of every goalie from Sweden since 1990, with league-average adjusted save percentages normalized to .914:

Two things stand out from that chart:

1. Sweden has really blossomed as a goalie producing country over the last decade (15 of the 23 Swedish goalies to ever play in the league have made their debut since the 2005 lockout).

2. The save percentage numbers are quite mediocre for the group as a whole, with the exception of the outstanding Henrik Lundqvist.

Wednesday, April 15, 2015

Predicting Playoff Success

From Alan Ryder's Ten Laws of Hockey Analytics:
One important warning - do not confuse correlation with causation.  The former is easy to prove, the latter is quite challenging.  For example, carry-in zone entries yield more scoring chances than do dump-in zone entries.  But this could mean that a carry-in is evidence of better neutral zone puck control rather than a cause of better offensive zone puck control.
Which of these variables do you think is the best predictor of playoff series winners in the NHL between 1984 and 1990?  In other words, if you were betting on matchups back then and could only look up one stat for each team to influence your decision, which is the one that would most frequently point to the eventual victor?
  1. Goals For
  2. Goals Against
  3. Shot Differential
  4. Team Shooting Percentage
  5. Ratio of Shorthanded Goals For vs. Against
It's gotta be #3, right, based on what we know about the importance of possession?  Or maybe #1 or #4, since offence had to be important in a league that was wide open and high-scoring?  Or perhaps that old saw about defence winning championships held true, and it was really #2?  The one that seems most out of place is #5, a variable measuring rare events that doesn't take into account anything that happens during the game's most frequent and important game situation (even strength).

But if we look at the numbers after the jump, we get some surprising results:

Thursday, April 9, 2015

Arbitrary Endpoints, Career Numbers, and the Future of Jacob Markstrom

(As an introductory note, it's been a while since I posted here, but a lot has happened in the interim, not just on the ice during the 2014-15 season but especially off of it, with the Summer of Analytics, the emergence of new statistical resources, and some interesting perspectives on goaltending from Steve Valiquette, Chris Boyle, and others. On top of all that, I was also inspired by attending the Ottawa Analytics Conference and meeting many of the people I have worked with and interacted with online.  All that means I'm planning to get back into hockey analytics, which for the time being will include contributing to the Hockey Prospectus Annual and blogging in this space.  Although I was pretty fortunate in having my last post here be on a topic that makes me look pretty good in hindsight (Dubnyk vs. Scrivens), it's long past time to starting pushing that one down the page.)

One of the things I have been thinking about lately, and something I wanted to bring up in my first post back, is the issue of career stats and arbitrary endpoints, to borrow a term used by ESPN sabermetrician Keith Law.  Here's the description from Law's glossary:
#arbitraryendpoints: Also known as cherry-picking, this means choosing one or both endpoints on a series of games to try to analyze a player. I’ve argued that it’s not arbitrary if the endpoint is tied to something specific, like a change in mechanics, an injury, or a recall from the minors, but even so, it’s always dangerous to throw out any data when you want to draw a conclusion.
I definitely agree that it is dangerous to throw out data and that it should never be done for the purposes of supporting an already-reached conclusion.  However, I also agree that it is not always arbitrary to look at splits and segments of data rather than relying on the complete sample if there is good reason to expect that some of the data is not representative of an athlete's true talent level.

There seems to be an increasing trend on Hockey Twitter for people to simply pull up a goalie's career save percentage or career EV SV% and use that as the final verdict on their talent level.  This can certainly be appropriate some of the time, perhaps even most of the time.  I still think that goaltending is above all else a results business, and that statistical measurements remain very powerful methods of evaluating performance.  That's why save percentage over a large sample size is usually a good proxy for a goalie's talent level.  However it is still only a proxy, and the three points mentioned by Law do also apply to goaltenders.  In the same way that Law might discount a pitcher's performance in his first year back from an arm injury, we might have reason to believe that a goalie could be deviating from his historical average because he is not yet at 100% health after coming back from some time off or has made some changes in his game after working with a new goalie coach.

On top of those factors there are others more specific to hockey goalies, such as team effects/shot quality, situational performance (e.g. EV vs. PK), home scorer bias/road performance, usage, etc.  These factors generally do not have a major impact on stats, but margins are so slim in goaltending that even a slight advantage or disadvantage can have an effect on the rankings.  Overall, I think sometimes insight can be missed by looking only at the big picture, and in those cases it is appropriate to take a deeper look.  And I'll start doing that by focusing a magnifying glass on the short but interesting pro career of Jacob Markstrom.

Thursday, January 16, 2014

Scrivens vs. Dubnyk

Just 1309 shots ago, Devan Dubnyk was a three-time Team Canada representative at the world championships making $3.75 million a year and seen as the future of goaltending in Edmonton, while Ben Scrivens was a backup goalie making $612K that started just 2 of his team's last 19 games before being included as the goalie going the other way in the Bernier deal.

How things change.  Dubnyk has struggled in 2013-14 (.894) while Scrivens has thrived on arrival in L.A. (.931), and as a result Edmonton's management figured it was worth pulling the trigger on two separate trades to effectively make that goalie swap.

I think there are might be a couple of legitimate reasons to prefer Ben Scrivens over Devan Dubnyk if one was forced to choose between the two of them (a cheaper cap hit being the main one), but I don't know why anybody would care that much.  It seems to be an obvious overreaction by the Oilers to their goaltending issues.

Both Dubnyk and Scrivens are 27 years old and pending UFAs.  Scrivens has a .917 career save percentage to Dubnyk's .910, but Dubnyk has almost 4 times the sample size at 5079 SA compared to 1365.  Over the past 4 seasons, Dubnyk's situational numbers aren't too far off Scrivens' (.920 EV, .876 PK vs. .923 EV, .891 PK), and that's despite playing on an Oilers team that averaged a 68 point pace over that span (including 34-70-15, .902 without Dubnyk in net).  Scrivens had better minor league numbers, but as a collegian he was more developed when he hit the pros whereas Dubnyk came from the Dub at the age of 20.  Dubnyk was a first round pick, while Scrivens was undrafted, and Dubnyk would likely have been considered ahead of Scrivens in development throughout their entire careers until a couple months ago.  I'm not sure half a season is enough to make a major correction in that relative ranking.

I find it very interesting that Nashville was the team acquiring Dubnyk, since the team's continued employment of Mitch Korn and track record of goalie development makes me generally trust their instincts on goaltending.  Dubnyk is going to have a good opportunity to turn things around with the Predators.

Even if the Oilers are right, though, what do they really gain by this move?  There are just 33 games left in another lost season, where the only real goal left to accomplish is to continue sinking faster than the Sabres and Flames and thereby gain the inside track on yet another first overall pick.  Ilya Bryzgalov is also still in the mix, and it seems likely he will get his share of starts, making acquiring a goaltending upgrade even less valuable to the team.

Assume that Oiler goalies other than Bryzgalov get 500 shots the rest of the way.  If Scrivens keeps up his .931, he'll allow about 35 goals, or 18 fewer than Dubnyk would have if he held steady on his seasonal pace over the same workload.  That's a sizable difference, equivalent to three wins in the standings, yet how likely is it that both goalies don't regress heavily towards their career averages, and what's the advantage in finishing 28th instead of 29th or 30th?  Even if they are philosophically opposed to tanking, if Edmonton is serious about handing the reigns over to Scrivens it would seem that they would have an awfully good chance of signing him this summer.  The Kings certainly aren't going to be much competition for any Edmonton offer given that they have their starting goalie locked up through 2023, and with Dubnyk's $3.5 million coming off the books Edmonton would likely have more than enough cash to outbid any other teams in Scrivens' pay range.  It appears they must be intending to give Scrivens a tryout to see if he merits a contract in July, but even if they do that they're making a decision from a fairly small sample size.

Then again, panicking over small samples seems to be something of an Oiler trademark.  If any team should be patient, you'd think it would be a team in development mode, yet the Oilers have been the king of goalie overreactions this season:

1. Signing Jason LaBarbera as the backup goalie, then dumping him to Chicago after only 146 shots against.

2. Bringing up minor-leaguer Richard Bachman and giving him three straight starts because he played pretty well in the first one.

3. Signing Ilya Bryzgalov, a goalie who nobody else wanted, to a one-year deal after Bachman got injured and Dubnyk and LaBarbera continued to struggle.

4. Trading Dubnyk and acquiring Scrivens.

The other big issue is the cost Edmonton paid to make the move.  They gave up a 3rd round draft pick (which given the Oilers' poor play will be a very high 3rd), plus they retained $1.75 million in salary on Dubnyk, plus they took on the contract of Matt Hendricks, who is signed for $1.85 million for the next three seasons.  Hendricks is 32 years old and has a -0.3 GVT this season and just 21 points in his last 170 games. Given his age and recent performance, he's very likely to be a replacement level player at best over the next three seasons, which means the Oilers are probably wasting about $4 million compared to signing an equivalent guy to the league minimum to plug in on their fourth line.  The Oilers did save the difference in salary between Dubnyk and Scrivens over the rest of the season (~$1.2 million), but with the retained salary and likely overpay on Hendricks it looks to me like they may have paid in the range of $4 million plus a 3rd rounder for 33 games of a goalie that they could have had for free this summer.  All in all, a perplexing move for Edmonton.

Goalie Utilization at the Olympics

From the reports I heard, Mike Babcock is looking to pick one goalie as his starter and run with him, rather than auditioning several goalies out during the preliminary rounds.  I think that makes sense, because trying to find the hot goalie is probably little more than shooting in the dark to begin with, and it's better to just throw your chips in on the best guy.

EV SV% since 2010-11:
Luongo .928
Price .926
Smith .926

EV SV% since 2012-13
Price .927
Smith .923
Luongo .922

There's probably not that much between Canada's goalies.  Chris Boyle has made the data-supported argument that Price has faced more difficult shots, which I certainly find interesting, and with his slight advantage in recent play and his strong form this year I do think Price should have the inside track on being the guy in Sochi.

That said, the compressed Olympic schedule means that it likely would not be sensible to start one goalie all the way through.  Canada plays 3 games in 4 days in the preliminary round, and if they don't earn a first round bye and have to go through the qualification game, then they would be looking at another 3 games in 4 days just to get through to the semifinals.  A semifinal loss means a bronze medal game the day after, while at least the gold medal game participants get a much-needed day of rest prior to the final showdown on Feb. 23.

Given the data on goalies making back-to-back starts, and considering that most countries have at least two quality netminders on their rosters, the argument could be made that few if any countries should be starting the same goalie in back-to-back games.  Canada should be in good shape no matter what they do against Norway and Austria, since you'd expect those to be easy wins and likely a light workload for their goaltender regardless, but it would probably be a good plan to split those starts.  And while it would be an extremely gutsy decision by any coach who elects to do so, if Canada ever got to a qualification game against one of those teams or another weak sister nation like Latvia or Slovenia, there would at least be an argument for the team to start their backup goalie and save the real starter for the quarterfinal the next day.

I really doubt any team would actually do this because if it ever backfired the coach would be raked over the coals, and you'd probably create all kinds of controversy by switching back and forth between goalies because everyone wearing a media badge loves to pounce all over that kind of manufactured drama.  No teams tried this at the last Olympics, as all 4 qualification game winners put the same netminder right back between the pipes for the quarterfinals.  That said, this strategy would make the most sense for a powerhouse team like Canada, because it would seem to have the least risk.  Goaltending didn't matter in the 8-2 playoff win over Germany in Vancouver, it seems almost certain that Canada would have ran away with  the game if either Brodeur or Fleury were tapped ahead of Luongo.  As it happens goaltending didn't really matter against Russia either, because of Canada's outstanding offensive display in scoring 7 goals, but it's not hard to envision an alternate scenario where Luongo's 25/28 would be not good enough to advance.  Don't even bother try to imagine one, just go back four years prior to when Brodeur's 31/33 QF against the same opponent resulted in a disappointing early exit for Canada.

I'll be watching Olympic goaltending decisions with interest, both in terms of why plays and when.  I'm expecting pretty conventional decision-making all around, but if anybody decides to think outside of the box I'll be impressed, whether it works or not.

Tuesday, January 14, 2014

One Shining Moment

I used to be much more of a baseball fan than I am right now, but on occasion I can get suckered in binge reading Joe Posnanski or someone like that, particularly in the middle of one of the sport's classic debates between sabermetricians vs. traditional media members.

Jack Morris' Hall of Fame candidacy has been one of those types of affairs, a 15 year debate about the value of a durable pitcher with a few shining postseason heroics but fairly underwhelming overall numbers. Plenty of different rationales have been offered by the pro-Morris camp, but I think that as much as any recent athlete I can think of, Morris is simply defined by a few big moments (most notably game 7 of the 1991 World Series), and the residual impact of those highlights trump all other factors in the minds of those who tend to rank players based on their gut feel as opposed to a detailed comparative analysis of their performance record.  Many of the arguments in favour of enshrining Morris seem to be people reaching for justification to support their already decided position.  That can of course be fairly criticized for being poor analysis, but I don't think you are going to convince many people purely by calling out their analysis, especially when they are being largely driven by subjective perceptions.

I think the power of the shining moment can be just as significant in hockey, perhaps even more so given the overwhelming importance of the Stanley Cup playoffs.  Just as with pitchers in baseball, winning or losing tends to stick with goalies in that it is easier to recall the successful plays of the winner and the negative ones of the loser.

One of my personal favourite examples of this is Marc-Andre Fleury in the 2009 playoffs.  Many hockey fans called him clutch and said he made the big save at the right time, because they could easily recall his stop on Lidstrom with time running out in the Finals in game 7, along with his breakaway save on Ovechkin and a few stops against the Flyers in round one.  But the rest of Fleury's playoffs were pretty ordinary (.908).  Nobody is able to fully recall even a small sample of shots like the 686 Fleury faced that postseason, it's going to inevitably filtered down to a few memorable ones and if the ones that stick are saves a goaltender will come off looking good.

I also think it people took longer to figure out Ondrej Pavelec was actually a pretty mediocre goalie because of his propensity to make the big highlight reel saves.  Fans would be travelling home from a game thinking of that one he snatched out of mid-air and not about the fact that he let in 4 out of the other 29 shots against, but it is how many you let in out of how many chances that really matters.

On the other hand, negative perceptions can be similar.  Tony Esposito seems to be remembered much less fondly by many older hockey fans than his overall record would suggest, and it doesn't take long at all in any discussion of his merits before somebody brings up Jacques Lemaire scoring on him from center ice in game 7 of the Finals.  Tommy Salo wasn't an all-time great, but he was a solid NHLer with an impressive international carer even though it remains awfully hard to think of him as even a competent netminder at this point because of the taint of that one Belarus goal influencing our collective memories.  I think that is how bad-team goalies tend to be forgotten and dismissed, it was always curious to me when someone like Allan Bester was treated as a punchline despite fairly impressive stats, but if you can't think of a goalie making a big save or winning something then you're probably going to think of some bad goal or another.  No matter how good they are, no goalie ever comes off looking good in a highlight reel of their goals against.

I believe countering this effect is one of the most important uses of the statistical record in evaluating athletes.  There are some legitimate quibbles about statistical recordkeeping and the reliability of various metrics, but at the same time all observers also have biases and faulty memory, and it's well worth having an extra check to ensure that the events our brains remember did actually happen in the way that we claim they did.  Maybe a player was clutch and "knew how to win", or maybe certain events stick in the memory more strongly than others.  The burden of proof should always be on the former position, in my opinion.