Peter Tanner has put together an incredible website for data, over at MoneyPuck.com. Many current sites house similar metrics used among analysts and hobbyists alike, each offering some unique piece of information that attracts different users.
MoneyPuck.com has incorporated some more intricate metrics, gleaned via NHL play-by-play files, lacking some of the finer microstats, like zone entries or passing. Those niche statistics are tracked by some individually and Corey Sznajder in bulk.
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The site contains detailed information incorporating expected goals among its typical metrics. A proprietary and intriguing metric presented is rebounds, and another measuring flurry adjustments. The link directs to the methodology and intricacies of these adjustments to conventional metrics and I’d recommend visiting the entire write up for more details. Nonetheless this is the equation for flurry adjustments lifted from the site.
The definition of a flurry adjusted expected goal is:
Flurry Adjusted Expected Goal Value = Chance of Not Scoring in Flurry Yet * Regular Expected Goal Value of Shot
Good scoring teams can incorporate rush, rebounds and active forechecking to be effective in every facet of offensive zone attack.
Which brings us to the Carolina Hurricanes, those Storm Surge aficionados of post-game entertainment.
They’re more than just an entertaining ‘storm surge’ and they’re a great example of how lots of shot attempts and shots led to their current success. Rebounds were inevitable to become relevant due to shot volume.
Isolating the shot dominating Hurricanes has a benefit of illustrating shooting from all areas of the ice, and its effect on expected goals and real goals. Using the data from MoneyPuck.com, we can create a rolling 10-game moving average of rebounds, and then compare to shot totals, and goals.
Tanner expanded his rebound metrics to incorporate expected goals. For example, ‘xGoalsFromxReboundsofShots’ is defined as follows:
Expected Goals from Expected Rebounds of player's shots. Even if a shot does not actually generate a rebound, if it's a shot that is likely to generate a rebound the player is credited with xGoalsFromxRebounds
We will expand on these shortly using the 2018-19 Hurricanes.
Using data at 5v5, it shouldn’t come as a surprise to see Carolina at the top of the league ranks for rebounds at even strength. Among the teams listed, leaders of each category are highlighted in yellow. Vegas, a great example of a pressing and swarm philosophy, and the Leafs buzz the net with enough talented shooters to create plenty of rebounds/60 minutes.
The data above was a culmination of individual lines of production. Expanding the dataset to identify the top lines producing rebounds and the results show the Martinook-Wallmark-Svechnikov unit leading the team by more than two times the nearest trio.
The tandem are league leaders with 43 rebounds, in a substantially less amount of ice time in comparison with lines from the across the league. Omitting the Hurricanes line, which has skated 271 minutes together, the rest of the lines in the next table have spent 36752 seconds on the ice together on average – the equivalent of 612 minutes.
Carolina Hurricanes and Rebounds
The chart below shows the rolling 10-game moving average of the Carolina Hurricanes rebound generation, expected rebounds and rebound goals across the top chart, while synched with a 10-game moving average of the Hurricanes shots by danger type, high, medium and low in the below chart.
We can see with the first vertical line how the Canes peaked at generating rebounds just before December 2018, which coincides with shots peaking in the medium danger zone. To me, this makes sense intuitively but should be studied further for any potential overall effect, including these factors:
- Low danger shots likely are saved and held by the goaltender, produce few rebounds, get blocked, or miss the net and less conducive to rebound generation. Point shots come into play here.
- High danger shots are most likely the cleanest to go into the net without producing a rebound, but could potentially ignite the flurry metric should there be scrambles for loose pucks – which is part of the makeup of high danger chances.
- Medium danger shots are quick chances likely to produce a rebound due to the goaltender requiring pre-shot movement, setting and getting square to the shooter, clean shots/attempts with defenders out of position.
There’s a noticeable decline in rebounds as the Canes began to take less medium range shot attempts, and further influenced by a dip in high danger shot attempts, with a slight increase from low danger shooting. The second vertical line elucidates the upswing in rebounds once again with the increase in medium range shooting.
There’s a sense the xReboundsFor line is influenced by the MDCF line and HDCF line, more than shooting from the point or low percentage areas. So when the puck gets to the point and everyone is yelling ‘shoooooot’, they should be yelling ‘get the puck to the medium scoring chance area’ … but that’s just too long.
The above isolated shot attempts and rebounds, but the chart below contains only shots on goal. Once again, two vertical lines outline the increases and decreases in the rolling average.
Expected Goals from Expected Rebounds
Tanner applies expected goals logic to rebounds (and flurry, but we are concentrating on rebounds), which produces two metrics outlined in the expected goals off rebound 10-game moving average. The metric xGoalsFromActualReboundsOfShots calculates expected goals from observed rebounds. The metric xGoalsFromxReboundsOfShotsFor calculates the expected goals from the metric of expected rebounds. Similar to the chart above, the Hurricanes really capitalized on burying rebounds during peak time in rebound generation this season.
If there’s a clear takeaway it’s limiting point shots unless there’s a chance to get in closer. Clearly, scoring takes precedence, but to increase the odds of scoring, using rebounds, and with traffic in front of the net, take advantage of loose pucks, its’ better to step into a better scoring area. Defensemen are playing the gap between goaltenders and the slot and there’s more room for stray forwards net-front at times.
A more in-depth study here would be a good start. The strategy involved in getting shots from medium danger shooting areas likely involves cycling and getting pucks out into open ice from the boards. Perhaps a slotline or royal road pass forcing goaltender pre shot movement and switching sides to move players out of position.
Shooting from the point – or at least blasting a shot through – is for the sake of firing howitzers into the net. That’s an old style scoring mindset, where an effective shot directed towards the goal could have the desired effect to generate a rebound – and more potential chances for a goal being scored.