• Big Oilers Data X: Isolating A Problem

    by  • May 24, 2013 • Hockey • 8 Comments

    This is part of a series looking for reasons for the Oilers Corsi% collapse in 2012-13 by examining things on a shift-by-shift basis. Part 1 can be found here. Part 2 can be found here. Part 3 can be found here. Part 4 can be found here. Part 5 can be found here. Part 6 can be found here. Part 7 can be found here. Part 8 can be found here. Part 9 can be found here.

    I’m sort of unhappy with the way I presented the information in the last post. While the shift concept is great analytically for individual players, I’m not really comfortable mashing things together like that. The problem with looking at what happens after NZ faceoffs the way that I did it is that it’s not really reflective of the mix of player shifts (ie. Hall plays more shifts than Petrell) and it’s kind of duplicative. It’s not terrible as a sort of first cut look at things, a way to identify problems, but with the data that I’ve gathered, I can do better.

    I decided to cut at this a different way. Rather than look at individual data, I just looked at what happened in the 45 seconds following a neutral zone faceoff (or until the next neutral zone faceoff, whichever comes first). Again, I did this for 2011-12 and 2012-13. I sorted the NZ faceoffs by who won them (Oilers or the opposition) and then calculated the Corsi% for those NZ faceoffs.

    OK, so right away it looks like one of my observations is, in fact, borne out. The Oilers didn’t really get appreciably worse in situations following an NZ loss this year – the opposition went from a 59.7% Corsi% to 59.9%. There was, however, a notable dip in their Corsi% following NZ wins, from 52.6% to 48.3%.

    A quick word about how much this matters. The Oilers had 1816 SAF and 2262 SAA this year, a Corsi% of 44.5%. In the 45 seconds following NZ faceoff wins, they had 157 SAF and 168 SAA. If they had last year’s Corsi% and the same number of shot attempts were involved, they would have been +172 and -153. If you factor that into the overall Corsi%, it would bump it to 44.9%. Half a point. If the Oilers put up the robust 59.8% Corsi% that their opposition has averaged against them over the past two years, they’d gain a full point. We’re talking about very small, discrete pieces of a hockey game here. You know that old saying about taking care of the pennies and the pounds take care of themselves? This is the pennies. They add up though.

    The table at left summarizes the SAF data in the 45 seconds after an NZ faceoff. It’s sorted by the team that won the draw. So, for example, in 2011-12, Edmonton won 641 draws. Of those 641 wins, they failed to get an SAF in the next 45 seconds on 428 occasions, had one SAF on 151 occasions and two or more SAF 62 times. Overall, they got an SAF 33.2% of the time and, on those occasions on which they got at least one SAF, they went on to get a second SAF 29.1% of the time.

    Looking at that, there doesn’t really seem to be a lot of change year-over-year. The Oilers’ opposition had kind of robot-like consistency. Edmonton did experience a slight increase in their 1 SAF% and a somewhat larger drop in their 2+ SAF% but it’s not huge. However, as Vic Ferrari says, the puck has to be somewhere, so let’s take a look at the other side of things.

    Hmm. Now that’s more interesting. The Oilers 2011-12 and the opposition’s 2011-12 and 2012-13 seasons look awfully similar. Edmonton was slightly more likely to allow an SAA on a given NZ win and very slightly more likely to allow additional shots, given that one shot has occurred. It’s awfully similar though. This year though – wow. A big spike in the percentage of NZ wins that were followed by an opposition SAA and a huge spike in the multi-SAA percentage.

    Let’s try putting what the data shows into a sentence or two: The Oilers were slightly more likely to generate an SAF this year in the 45 seconds after an NZ faceoff win than they were last year. They were slightly less likely to generate multiple SAF. They were markedly more likely to allow an SAA and even more likely to allow multiple SAA once they had allowed the first one.

    When I try to imagine in my head what this might look like if it was converted from an Excel spreadsheet into the form of a hockey game, I get an image of a team that’s about the same when it comes to moving from winning the faceoff to entering the offensive zone to creating a shot but got worse at preventing the other team from recovering the puck, heading down the ice, entering the Oilers’ zone, creating a shot attempt and then creating another shot attempt.

    Let’s say that I was right about what that would look like. How would this appear in the data? Well, we might see that 2011-12 and 2012-13 would look similar for the Oilers up to some point and then the opposition’s numbers would explode. I’ve put together a data table summarizing some key data through the first twenty seconds after an NZ faceoff win for the Oilers and their opponents for 2011-12 and 2012-13.

    (Note: “SA/60″ means “shot attempts/60″ not “shots against/60″ as is common.)

    It looks awfully similar. There’s a consistent Corsi% difference for the Oilers – other teams are better at converting neutral zone faceoff wins into Corsi% but that doesn’t seem entirely surprising. Note how similar the volume of shot attempts is – the puck has to be somewhere, in this case, it has to be moved through the neutral zone. The average shot attempt volume at 5v5 is something like 100 or 105; the twenty seconds after a neutral zone faceoff win are a bit of a dead space in a hockey game, which seems reasonable – the team that starts with possession of the puck is a ways from the offensive zone. Now let’s look at what happened in seconds 21 to 45 after a neutral zone faceoff.

    Well. That’s quite something. There’s a veritable explosion of shot attempts at the Oilers net this year 21 to 45 seconds after a neutral zone faceoff has occurred. It’s up like 31%. You can see that the volume of shot attempts has increased significantly as well. This is, I think, consistent with what I said above:

    When I try to imagine in my head what this might look like if it was converted from an Excel spreadsheet into the form of a hockey game, I get an image of a team that’s about the same when it comes to moving from winning the faceoff to entering the offensive zone to creating a shot but got worse at preventing the other team from recovering the puck, heading down the ice, entering the Oilers’ zone, creating a shot attempt and then creating another shot attempt.

    That seems to be exactly what happened. A minor Corsi% change in the first 20 seconds, followed by a big Corsi% change in the next 25 seconds that’s tied up with a huge spike in the rate of shot attempts allowed. Let’s assume that there was some sort of a tactical thing that led to this for a moment. If you assume that, absent the tactical change, there would have been 100 SA/60 and that it would have been a 49.8/50.2 split, twenty shot attempts against disappear. The Oilers’ Corsi% bumps up from 44.5% to 44.8%. There’s more to it than that though – doing a better job of preventing the other team from coming down the ice means fewer faceoffs in the Oilers end, which means fewer situations in which the other team has a very high expected Corsi%. There’s a kind of knock-on effect here, I suspect. Let’s just check that:

    Bingo. The effect is going to be larger than just the immediate bump in shot attempts against. It leads to more defensive zone faceoffs, which leads to more shot attempts against, which likely leads to more defensive zone faceoffs and the next thing you know you’re getting Jerred Smithson in exchange for a fourth round draft pick because he’s good at winning defensive zone faceoffs.

    I’ve got two different directions I think I can go from here. Young Willis has graciously provided me with his zone entry data and it’s worth looking at this aspect of play through that lens. However, if you’ve been following this series, you’ll recall that I pointed out that there was a similar collapse in Corsi% on offensive zone faceoff wins as with neutral zone faceoff wins.

    I’m wondering whether that might have a similar profile to the neutral zone faceoff win collapse and think I might have a hard look at that next. I think I’ve made a reasonably strong case that there was something happening in that 21-45 second window following a neutral zone faceoff win – if there’s something similar happening in a defined period after an offensive zone faceoff win, then we’re probably really on to something.

    Email Tyler Dellow at tyler@mc79hockey.com

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    8 Responses to Big Oilers Data X: Isolating A Problem

    1. Trentent
      May 24, 2013 at

      So the Oilers got Smithson to stop the bleeding but they had no idea where they were bleeding from?

      I guess tape needs to be examined at this point in an attempt to quantify what play (aka, coaches fault) or players (aka, blackholes) were the root cause?

    2. Tyler Dellow
      May 24, 2013 at

      I’m being a bit tongue in cheek with that Smithson comment. That being said, the problem looks more to me like one of too many faceoffs in the defensive zone. Not winning enough of them is kind of a secondary problem.

    3. Pierce Cunneen
      May 24, 2013 at

      Tyler, correct me if I’m wrong but I think the last two column labels for your second second chart (not counting the bar graph) are incorrect

      • Tyler Dellow
        May 24, 2013 at

        Bah – thanks Pierce. Should be SAA not SAF.

    4. Pierce Cunneen
      May 25, 2013 at

      Tyler,

      So it seems that one of the conclusions we are seeing from your data is that the Oilers are doing something wrong about 20 seconds after the Neutral zone faceoff win. So whatever the Oilers are doing wrong doesn’t actually have anything to do with the faceoff but more to do with other aspects of play. While I would not know where to begin concerning the Oilers (I’m a flyers fan myself so I don’t get a ton of time to watch the oilers), I am betting that zone entries will tell us more of the story.

      My bet (without watching the oilers) would be that at around the 20 second mark is when the puck generally will have left the offensive zone of the oilers and gotten back into the Neutral zone. Thus, the poor performance 20 seconds after the face off win is an illustration that the Oilers are losing the battle of the Neutral zone, probably allowing their opponents to win the neutral zone more frequently and possibly carry the puck into the Oiler’s D zone with possession (which has been shown to drastically increase shots as opposed to old-school dump and chase).

      So this doesn’t seem to be a face off problem or what they do immediately after the face-off but rather a neutral zone problem.

      • woodguy
        May 26, 2013 at

        20 seconds is about the right amount of time to: (after FO win)

        -Dump the puck in instead of carry it
        -Fail to retrieve it
        -Dman pinch (and miss) to try to keep the puck in the ozone
        -Give up an odd man rush

        • Pierce Cunneen
          May 26, 2013 at

          exactly. This seems to point towards a neutral zone problem, rather than a face off problem.

    5. Pingback: The Edmonton Oilers made the right call in dismissing Ralph Krueger | Edmonton Journal

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