Goaltending and Hockey Analytics – Linked by a Paradox?

There may be an interesting paradox developing within hockey. The working theory is that as advanced analysis and data-driven decision-making continue to gain traction within professional team operations and management, the effect of what can be measured as repeatable skill may be shrinking. The Paradox of Skill suggests as absolute skill levels rise, results become more dependent on luck than skill. As team analysts continue (begin) to optimize player deployment, development, and management there should theoretically be fewer inefficiencies and asymmetries within the market. In a hypothetical league of more equitable talent distribution, near perfect information and use of optimal strategies, team results would be driven more by luck than superior management.

Goaltenders Raising the Bar

Certainly forecasting anything, let alone still-evolving hockey analytics, is often a fool’s errand – so why discuss? Well, I believe that the paradox of skill has already manifested itself in hockey and actually provides a loose framework of how advanced analysis will become integrated into the professional game. Consider the rise of modern goaltending.

Absolute NHL goaltender ability has continually increased for the last 30 years. However, differential ability between goaltenders has tightened. It has become increasingly difficult to distinguish long-term, sustainable goaltender ability while variations in results are increasingly owed to random chance. Goalies appear ‘voodoo’ when attempting to measure results (read: ability + luck) using the data currently available – much like the paradox of skill would predict.[1] More advanced ways of measuring goaltending performance will be developed (say, controlling for traffic and angular velocity prior to release), but that will just further isolate and highlight the effect of luck.[2]

Spot the Trend Data courtesy of hockey-reference.com
Spot the Trend
Data courtesy of hockey-reference.com

Will well-managed teams create a similar paradox amongst competing professional teams in the future? Maybe. Consider such a team would maximize the expected value talent acquired, employ optimal on-ice strategies, and employ tactics to improve player development. Successful strategies could be reverse engineered and replicated, cascading throughout the league – in theory. Professional sports leagues are ‘copycat’ leagues and there is too much at stake not to adopt a superior strategy, despite a perceived coolness to new and challenging ideas.

Dominant Strategies“I don’t care what you do, just stop the puck”

How did goaltending evolve to dominate the game of hockey? And what parallel pathways need to exist in hockey analytics to do the same?

  1. Advances in technology – equipment became lighter and more protective.[3] This allowed goaltenders to move better, develop superior blocking tactics (standing up vs butterfly), cover more net, and less worry of catching a painful shot. The growth of hockey analytics has been dependent on web scraping, automation, and increasing processing power and will soon come to rely on data derived from motion-tracking cameras. Barriers to entry and cost of resources are negligible lending all fanalysts the opportunity to contribute to the game.
  2. Contributions from independent practitioners – The ubiquitous goaltending coach position is a relatively new one compared to most professional leagues. In the early 2000s, I was lucky enough to cross paths with innovative goaltending instructors who distributed new tactics, strategies, and training methods available to young goaltenders. Between their travel, camps, and clinics (and later their own development centers) they diffused innovative approaches to the position, setting the bar higher and higher for students. A few of these coaches went on become NHL goalie coaches – effectively capturing a position that didn’t exist 30 years prior. Now the existence of goalie coach cascade down to all levels of competitive hockey.[4]  Similarly, the most powerful contributions to the hockey analytics movement have been by bright individuals exposing their ideas and studies to the judicious public. The best ideas were built upon and the rest (generally) discarded. Will hockey analytics evolve (read: become accepted widely among executives) faster than goaltending? I don’t know – a goaltending career takes well over a decade to mature, but they play many games providing feedback on new strategies rather quickly.[5] Comparatively, ideas develop quicker but might take longer to demonstrate their value – not only are humans hard-wired to reject new ideas there are fewer managerial opportunities to prove a heavy data-driven approach to be a dominant strategy.
  3. Existence of a naïve acceptance – The art (and science) of goaltending is not especially well understood among many coaches, particularly with relative skill levels converging. However, managers and coaches do understand results. Early in my career, I had a coach who was only comfortable with stand-up goaltenders, his own formative experiences occurring when goaltender predominately remained erect (in order to keep their poorly padded torso and head from constant danger). However, he saw a dominant strategy (more net coverage) and placed faith in my ability without a comprehensive understanding or comfort of modern goaltending. Analytics will have to be accepted the same way – gradual but built on demonstrated effectiveness. Not everyone is comfortable with statistics and probabilities, but like goaltenders, the job of analysts is to produce results. That means rigorous and actionable work that offers a superior strategy to the status quo. This will earn the buy-in from owners and senior management who understand that they can’t be at a competitive disadvantage.

Forecasting Futility

Clearly the arc of the analytics evolution will differ from the goaltender evolution, primary reasons being:

  • Any sweeping categorization of two-decade-plus ‘movement’ is prone to simplification and revisionist history.
  • While goaltending as a whole has improved substantially, incremental differences in ability still obviously exist between goaltenders. In the same way, not all analysts or teams of analysts will be created equal. A non-zero advantage in managerial ability may compound over time. However, the signal will likely be less significant than variation in luck over that extended timeframe. In both disciplines, that rising ability may give way to a paradox of not being able to decipher their respective skills, muddying the waters around results.
  • Goaltending results occur immediately and visibly. Fair or not, an outlier goaltender can be judged after a quarter of a season, managerial results will take longer to come to fruition. Not only that, we only observe the one of many alternative histories for the manager, while we get to observe thousands of shots against a goaltender. Managerial decisions will almost always operation under a fog of uncertainty.

Alternatively, it important to consider the distribution of athlete talent against those of those in the knowledge economy. Goaltenders are bound by normally distributed deviations of size, speed, and strength. Those limitations don’t exist for engineers and analysts, but they do operate in a more complex system, leaving most decisions to be subjected to randomness. This luck is compounded by the negative feedback loops of the draft and salary cap, it is unlikely a masterfully designed team would permanently dominate, but it suggests some teams will hold an analytical advantage and the league won’t turn into some efficient-market-hypothesis-all-teams-50%-corsi-50%-goals-coin-flip game. But if a superstar analyst team could consistently and handily beat a market of 29 other very good analyst teams in a complex system, they should probably take their skills to another more profitable or impactful industry.

xkcd.com
xkcd.com

Other Paradoxes of Analytics

Because these are confusing times we live in, I’d be remiss if I didn’t mention two other paradoxes of hockey analytics.

    • Thorough, rigorous work is often difficult to understand and not easily understood by senior decision-makers. This is a problem in many data-intensive industries – analytical tools outpace the general understanding of how they work. It seems that (much like the goaltending framework available to us) once data-driven strategies are employed and succeed, all teams will be forced to buy-in and trust that they have hired competent analysts that can deliver actionable insights from a complex question. Hopefully.

  • With more and more teams buying into analytics, the some of the best work is taken private. The best work is taken in-house seemingly overnight, sometimes burying a lot of foundational work and data. That said, these issues are widely understood and there is a noble and concerted effort to maintain transparency and openness. We can only hope that these efforts are appreciated, supported, and replicated.

 

Final Thoughts

The best hockey analysis has borrowed empiricism and data-driven decision-making from the scientific method, creating an expectation that as hockey analytics gain influence at the highest levels, we (collectively) will know more about the game.[7] However, assuming the best hockey analysts end up influencing team behavior, it is possible much of the variation between NHL teams[8] will be random chance – making future predictive discoveries less likely and weakening the relationship of current discoveries.

Additionally, when it feels like the analytical approach to hockey is receiving unjustified push back or skepticism, it is important to remember that the goaltender evolution, initiated by fortuitous circumstance, eventually forced buy-ins from traditionalists by offering a superior approach and results. However, increasing absolute skill in a field can have unintended consequences – relative differences in skill will decrease, possibly causing results to become more dependent on luck than skill. Something to consider next time you try to make sense of the goaltender position.

 

[1] This is not to say all goalies in 2016 are of equal skill levels, but they are absolutely more talented than their ancestors and fall within a smaller range of abilities. That said, outside of a top 2 or 3 guys, the top 5-10 list of goalies is a game of musical chairs, quarter to quarter, season to season.

[2] Goaltenders don’t get a chance to ‘drive the play,’ so it is very important to control for external factors. This can’t be done comprehensively with current data. Even with complete data, it may be futile.

[3] And cooler, possibly attracting better athletes to the position, your author notwithstanding.

[4] Another feature of the paradox of rising skill levels: to fail to improve is the same as getting worse. Hence, employing a goalie coach is necessary in order to prevent a loss of competitiveness. The result: plenty of goalie coaches of varying ability, but likely without a strong effect on their goaltender’s performance. This likely causes some skepticism toward their necessity. This is probably a result of their own success, they are indirectly represented by an individual whose immediate results might owe more to luck than incremental skill aided by the goalie coach.

[5] For example, a strategy devised at 6 years old of lying across the goal line forcing other 6 year-olds to lift the puck proved to be inferior and was consequently dropped from my repertoire.

[7] Maybe even understanding the link between shot attempts and goals (you can read this sarcastically if you like).

[8] And other leagues that are able to track and provide accurate and useful data.