The following is data is all at 4-on-5 with both goalies in their nets. A special thanks to Evolving Hockey for data and their scraper.
In March of 2019, Mike Pfeil coined the term “powerkill” at the Seattle Hockey Analytics Conference. It was much more of a small excerpt from his whole presentation, but it seemed to motivate Meghan Hall and Alison Lukan. In the coming months, Lukan would write about how the Columbus Blue Jackets utilized an aggressive approach in their penalty killing system, while Hall would present at RITSAC and OTTHAC before they finally came together to present at the Columbus Blue Jackets Hockey Analytics Conference in February.
Looking to continue researching this phenomenon, I set out to answer a few questions I had. In order to give shots some added context beyond what the NHL’s public data supplies, throughout the last few months, I tracked shot assists and where possessions leading to shots had started. As a side benefit, I was also able to filter out shots that didn’t appear to exist, were recorded incorrectly, or where the possession started at 4-on-4.
In 2016, Matt Cane developed a metric to approximate penalty kill aggressiveness by combining penalty kill controlled and failed entries for, and dividing them by the entries a penalty kill faces from their opponent. The theory behind that being that penalty kills that attempt to control more entries into the offensive zone are inherently more aggressive. Hall and Lukan also found that a penalty kill’s rate of controlled entries has a strong correlation to the rate at which they take shots.
Part of the reason these two stats have such a strong correlation is that the vast majority of shots require a zone entry. Not including rebound shots, 82% of 4v5 shots stemmed from possessions starting outside of the offensive zone over the course of the 2019-20 season.
Also in 2016, Ryan Stimson began adding context to entries at even strength. He found that a shot following a controlled entry with at least one offensive zone pass went in significantly more often than if there was no offensive zone pass between the entry and shot. In order to replicate this, I looked at shooting percentage of offensive zone shots where the penalty killing team took possession outside of the offensive zone based on where the primary shot assist occurred if there was one.
Unsurprisingly, more than a fair share of 4v5 shots are unassisted, however, there appears to be a significant boost in shooting percentage among transition shots that are proceeded by a shot assist from the offensive zone. As a consequence, teams that create offensive zone shot assists at a high rate generally score at a higher rate.
While these are rather rare occurrences, making up only one-fourth of transition shots, teams should look to increase their pre-shot movement on shorthanded rush shots, but how do they do that?
Encouraging creativity is the first step. The Vegas Golden Knights displayed this beautifully on quite a few occasions.
Allowing players to be patient and work off of each other to find passing lanes can pay massive dividends. Shorthanded shots are rare no matter what, so why not try to make them as dangerous as possible? You may pass up on a few shots, but you could score more goals in the grand scheme of things.
It is also important that the defensemen jump into the rush when the opportunity is there. While the risk-averse thinker may be worried about an attack going the other way, the opportunist is looking to take advantage of the upward trend in four-forward powerplay units, leaving the opponent with only one defenseman on the ice to defend the rush.
In the clip above, the Vegas defenseman gave his forwards the time and space to set up a 2-on-1 by controlling the exit. Had the Vegas defenseman passed much earlier, it would’ve been much easier for the opposing defenseman to maintain a gap.
Having the defensemen jump into the rush also opens up the opportunity to include 5-on-5 entry concepts.
The middle drive is the most common and simple entry concept. The closest player drives to the net, often bringing a defender with them, while the third player into the play looks to find a cross-ice passing lane. The Sharks complete the cross-ice pass and are able to create a fairly dangerous shot from the high slot as a result.
An underneath concept, where the puck carrier and the closest player switch just before the blue line, can add another twist on things. Moreover, the Sharks still bring in their other defenseman the same way they would at even strength, offering a third passing option for the puck carrier. While it may appear to be risky having all four penalty killers in the offensive zone, it was crucial to extending possession in this case.
Goals are rare events in hockey, especially shorthanded. The rarity of shorthanded goals lengthens the amount of time it takes to derive any conclusions from them to the point that even an entire season is not long enough to dissolve much of the randomness behind them. However, understanding what controllable factors help create shorthanded goals, and applying them to your process, is important. We know that deploying better offensive players, controlling more entries, and passing after those entries all lead to more shorthanded goals over time.
Still, there is much more to learn about shorthanded offense and defense. That includes but is not limited to:
- Optimal forechecking formations
- Optimal in-zone formations
- Evaluating individual players
I highly recommend to anyone who is looking to get into hockey analytics to take one of these issues and run with it. For those who want to play around with the data I have tracked, it can be found here.