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26 January 2016: Anaheim Ducks defenseman Hampus Lindholm (47) keeps the puck in the offensive zone. The Anaheim Ducks defeated the Boston Bruins 6-2 in a regular season NHL game at TD Garden in Boston, Massachusetts. (Photograph by Fred Kfoury III/Icon Sportswire)

Using shot assists to dig deeper into NHL trends

Fred Kfoury III/Icon Sportswire

Using shot assists to dig deeper into NHL trends

Previously, I took at look at passing data created by Ryan Stimson and the NHL passing project. Specifically, I dove into Stimson’s work on primary shot assists – that is, passes immediately preceding a shot on goal, a missed shot, or a blocked shot (a Corsi).

Here, we’ll turn our focus to some more in-depth analysis of what the passing data might tell us about outliers, team systems, player positions, and ask some more questions about what else this data can tell us. To get started, I’ll turn to my usual device, interactive viz.

box-whisker fwds

*as usual, you can find this viz on my tableau profile by clicking here. It’s interactive – hover over dots to see additional player info.

This is a team-by-team breakdown of forwards with skaters ranked by their per hour shot assists rate. Henrik Sedin sets up teammates for a Corsi ~22 times per hour. The average forward creates ~9 shot assists per 60 minutes (ShA60). Devante Smith-Pelly provides almost zero shot assists.

I’ve chosen a box-and-whisker plot to highlight a couple of notes:

  • players that were “outliers” – their performance significantly outpaced (or lagged behind) their teammates
  • team patterns (for example, a small range of similarly performing players vs. a wide range of performances. Or, a team average considerably below/above the average skater’s rate)

Before we go on, a basic understanding of box-and-whisker plots is helpful. They’re not complicated, but this video does a good job of laying out basics as a refresher, just in case your last use was on an eighth grade data management assignment.

So, what do we see in this graph?

Box-and-whiskers calculate a median, a range, and then “whiskers.” Any data point that plots outside of the whiskers’ reach is an outlier because the value is very large/small relative to the other data in the group.

Take Anaheim as an example. Their median (where the two color shades meet inside the box) is at ~9 ShA60, which is the league average. Anaheim’s worst forward ShA rate belongs to Maroon, at less than 8 shot assists per hour.

Most interesting is that Ryan Getzlaf, regarded as one of the NHL’s best passers, is an outlier. His performance is so much stronger than that of his teammates (almost 15 shot assists per hour) that his plot is beyond the upper whisker.

The other positive outliers are a (mostly) predictable group; Krejci, O’Reilly, E. Staal, Versteeg, P. Kane, Toews, Spezza, Benn, Barkov, Jokinen, Gallagher, Ribeiro, Nielsen, Malkin, Crosby, Thornton, and Henrik “Passy” Sedin.

Negative outliers include some interesting NHLers; Terry, Di Giuseppe, McLeod, L. Shaw, and Smith-Pelly during his time in New Jersey (though note, he ranked lowest in Montreal before being traded by the Habs to the Devils).

In this year’s data, players that exceed the shot assist rates of their teammates are far more common than those who are extremely poor at passes leading directly to shots – by a factor of almost four-to-one. We’ll need more data to see if this is a pattern or not.

box-whisker def

*interactive viz can be found here.

We can complete the same analysis as above for defensemen. Before glancing, make a list of the best passing defensemen in the NHL. If you named Ekman-Larsson, Campbell, Yandle, Karlsson, and Letang, you’ve done well. If you also guessed that Toronto’s Jake Gardiner was a relatively exceptional passer, you’ve done well.

These are the outliers among defensemen in making passes that directly lead to shot attempts.

How about negative outliers? Again, there are far fewer than the positive outlier group. Quincey, Borowiecki, and Nick Schultz all produce significantly shot assists per hour than their fellow blue liners.

Looking into team systems

Much like any player rankings, checking in on the data set outliers is interesting because we can highlight the elite and deride those fringe NHLers for wasting space on a team’s roster. But this data can be used in myriad other ways as well.

Take, for example, the data on Anaheim’s defense corps. Their box spans from ~5 ShA60 to ~7 ShA60 (average ShA60 for a defenseman is about five per hour) with whiskers extending to just under 5 ShA60 and as high as ~8 ShA60. The Ducks had no outliers among their defensemen. It’s reasonable to say that Anaheim’s defensemen are an above average group in terms of passes leading to shots.

Working with that hypothesis, let’s check in on some film to note how the Ducks defenders are involved in the team’s offense.

1- Lindholm individual rush 1 - Ducks change, Stars have everyone back 1 - Lindholm loses puck

In mid-January, the Ducks played the Dallas Stars in Anaheim. Within the first two minutes of the game, the Ducks defensemen show that Boudreau’s game plan permitted or encouraged them to be aggressive through the neutral zone and into the offensive zone.

In the three stills above, Lindholm charges the offensive blue line even though his linemates are on a full change and the Stars have completely recovered into their defensive zone.

Lindholm loses the puck this time. That doesn’t stop the Ducks from trying.

2- still 4 ducks in view 2 - Vatanen enters zone with speed 2 - Vatanen walks to net front, scores

Shortly after, the Ducks penetrate the offensive zone and defenseman Sami Vatanen drives straight down the middle into the slot, scoring from in close. This play does show that the Ducks defense are permitted to take chances in the offensive zone to create scoring.

Still, this isn’t an example of a shot assist by Anaheim’s defensemen, so let’s keep moving.

8 - up 3-0, DEF pinch, contribute SA, goal 8 - DEF in slot to make 4-0 8 - Theodore

Still in the first, the Ducks have jumped to a 3-0 lead. Still, the defensemen remain activated. On this place, Shea Theodore (top-right in the second and third stills, marked by a yellow arrow in the third) joins the forwards, handling the puck in the slot. Theodore snaps a pass to Corey Perry (cruising past goaltender Kari Lehtonen’s left pad) and Perry taps in to put the Ducks up 4-0.

What’s most interesting here is that, rather than go into a ‘shell’ to protect the 3-0 lead, Anaheim’s defensemen continue pinching deep into the offensive zone to help generate offense.

One last play worth noting:

9 - up 4-0, Bieksa pinches --- again

After routinely pinching in from the blue line during the first period (including a tipped shot on goal from just above the crease) Bieksa slides down the wall, eventually going just deeper than the faceoff dots before firing a hard pass to the front of the net. No scoring comes from the play but the Ducks make clear that the defense are a key part of the offensive zone attack.

So, how does this link with the shot assists data?

Proceeding with the knowledge that Anaheim’s defense corps produces an above-average rate of shot assists, we can look in on specific in-game strategy to see why and how these shot assists are occurring. For the Ducks, head coach Bruce Boudreau relied on making his defensemen active and aggressive, both through deep pinches on the boards and net-drives down the middle of the ice.

The pinches and net-drives by the defense are clear enough but, with comparative data across teams, we can conclude that Anaheim employs this aggressive style of play more than most NHL teams.

Two thoughts bear mentioning here before concluding.

First, this is only one tracked period in a single game from last season. Watching many periods of many games would yield other insights and give us more confidence in what we have seen. However, the focus here is that this data set gives important (and comparative) clues about team strategy to allow for informed, hypothesis-drive analysis of game play.

Second, this kind of analysis could work backwards as well. After watching film and noticing a team’s proficiency (or deficiency) at creating shot assists, it’s possible to turn to the data to verify that the skaters are or are not skilled Corsi passers or to note how a given team compares with other teams.

Next, we’ll go beyond shot assist rates as a standalone statistic to put individual players in context. Using Stimson’s primary shot contributions stat, we will calculate how much each player drives on-ice offensive activity and move towards definitions of specific player styles.

For now, here’s a link to each team’s roster from last season with every player ranked by their shot assists per hour rates.

Sean Tierney uses stats and viz to write hockey stories. He doesn't have a favourite hockey team anymore. He's been called a "stats nerd" on more than one occasion and has been flattered every time.

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