Hello everyone, I’d like to start out by apologizing for the lack of activity on the blog over the off-season. It’s been a busy time for me because, as some of you may know, I’m currently in the middle of a project that involves me tracking zone entries & exits from all 1230 games of last year’s NHL season. My intention was (and still is) to track every game and release the data in an e-book and/or an online database for fans, bloggers and writers to do their own analysis. If you keep up with this blog or follow me on Twitter, you probably know that I’ve been doing this for the Hurricanes for the last two seasons and decided to start tracking the entire league around late-December so that a set for the entire league is available.
Why is it so important to have this data, though? The world of hockey analytics is growing by the second and there’s been some great research done using the data the NHL has available to the public, but it only goes so far. There’s been enough evidence presented done to show that shot-based metrics (or possession) are very important and arguably the most reliable data available in regards to what drives goals & wins. What makes players & teams be able to drive possession is still a work in progress, though. We know that skill & context (shown through metrics like zone starts & quality of competition) play a role in this. Zone entries are also critical when doing this analysis.
The idea of tracking zone entries was pioneered to the blogging world by Broad Street Hockey & hockey stats guru Eric Tulsky, who has been studying this for years and influenced me to start tracking this for the Hurricanes and a few other teams. In early 2013, Tulsky presented a study on zone entries at the Sloan Sports Analytics Conference and came to the conclusion that shot differential (or possession) at even strength is largely driven by the ability to carry the puck into the zone more frequently than their opponents. The general rule of thumb is that teams create more shots off controlled entries than they do off dump-ins, so players who can do this on a regular basis have a good chance of outshooting their opponents, winning the “possession battle” and put their team in a good position to win. When tracking entries, what I do is note when each team crossed the opposing blue line, how they did it (by carry, dump-in or other means) and the time which they did it. Tulsky also built a spreadsheet that automatically tabulates the number of non-blocked shots create off each entry, hence why we know controlled zone entries are more favorable to dump-ins.
This isn’t to say that dumping the puck in is a “bad” play by any means because there are some clubs who win the shot battle despite playing mostly dump-and-retrieve for most of the game. One of them being this year’s Stanley Cup champs. The Los Angeles Kings have been an elite possession team for years and have done it by playing mostly dump-and-chase hockey and forcing their opponents to do the same. Nick Chapin of Jewels From The Crown discovered this from tracking their zone entries this year. It speaks highly of the Kings defensive play and their ability to clog the neutral zone and make creating offense incredibly tough for their opponents.
The Kings still fit Tulsky’s hypothesis because they enter the zone with control more often than their opponents, but it’s interesting that they are able to maintain such a strong shot differential while playing a low-risk game. Are they a unique club or are there other teams like them who succeed at a similar tactic? This is where having zone entry data for every team can really help and it’s something that I am aiming to complete & publish before the new season begins.
I was hoping to have this released by now, but tracking these games takes a lot of manual labor on my part and I have run into some constant Internet outage issues that are beyond of my control, so the release date will end up being delayed. That said, I want to give everyone a progress report on this and give a little synopsis of what I’m doing. I spend most of my time trying to get as many games as possible tracked and haven’t been able to write much over the last couple of months, as you can imagine. Now that I’m currently stuck in another outage (never get Xfinity, folks), I figured it would be a good time to go into the details of this project, explain its importance and some discoveries you can make by using the data.
The real value that comes with having zone entry & exit data is being able to more clearly identify a problem area of your team, what is causing it and how you might be able to fix it. Tyler Dellow of mc79hockey recently used zone entries to show why the Devils create a low number of shots off faceoffs and I have also used them to explain some things that have gone on with the Hurricanes this past season. I’ve used zone entries to break down the team’s power play in a couple articles and have also tackled issues like why Jordan Staal’s line had trouble creating goals despite winning the territorial battle and how the Hurricanes struggled to prevent carry-ins late in the season.
What else can zone entries be used for, though? Let’s take one problem with the Hurricanes and see if we can find an answer.
Problem: The Hurricanes were a lousy possession team
There was a lot that went wrong with the Hurricanes this year, with the underlying issue being that they were a bad possession team. They controlled fewer than 50% of the shot attempts at 5v5 and were a bottom-10 team in the NHL at this during close-game situations. There were a few stretches where they improved but overall, the Hurricanes struggled to keep the puck out of their end and spent large portions of the game running around trying to defend instead of being on the attack. When they did get the chance to create offense, it never resulted in much (partially due to 6.8 shooting percentage among other factors) and they ended up being badly outscored when playing 5-on-5.
I’ve talked about some things that have influenced the Hurricanes goal-scoring issues, but the root of a lot of their problems stem from them being a bad possession team. How much does their play in the neutral zone have to do with it
One thing that immediately sticks out here is that the Hurricanes were outshot in basically all situations except on controlled entries They also carried the puck in on a fewer percentage of their entries than their opponents and were worse at generating shots off dump-ins. Going from Tulsky’s studies, we know that shots off controlled entries lead to more shots no matter who carries the puck in, so the Hurricanes would be better served to carry the puck in more often. They aren’t very good at creating shots when they have to go retrieve the puck and didn’t have the ideal personnel to play this style of game. I also find it interesting that the team’s defense didn’t see much of an improvement despite them playing more of a low-risk system and hindering their offense in the process. The team’s improved “defensive play” didn’t lead to much at all because they were still giving up more shots than they were creating and spending large segments of games trapped in their own end.
So, we know that neutral zone play was a big factor in the Hurricanes being a bad possession team. Which players were causing it? This is where the fun begins.
Control = % of Player’s entries with control, On-ice Control% =Team carry-in% when this player was on the ice, Shots/Entry = Shots per Entry, Shots/contr = Shots per controlled entry, Shots/dump = Shots per dump-in, Opp = Opponent, NZ% = Neutral zone Fenwick (Player’s expected shot attempt differential based on their performance in the neutral zone)
Knowing that the Hurricanes problems were that they didn’t carry the puck in enough and that they gave up more shots off entries than they created, we are looking for players with strong neutral zone scores. This speaks strongly of Jordan Staal, Nathan Gerbe & Alexander Semin, all of whom carried the puck in on more than 50% of their entries and posted very strong shot differentials off zone entries. On the other side of the coin, we have Eric Staal & Jeff Skinner, who were able to carry the puck in at a high rate but were destroyed in terms of neutral zone shot differential. Skinner’s neutral zone Fenwick is especially alarming because he has a bigger role here than almost anyone on the team and is very productive when it comes to getting shots on goal. Perhaps this suggests that his strong scoring chance & shot totals are the product of him starting a lot of his shifts in the offensive zone? It’s certainly possible, although the Hurricanes did create a high number of shots off his entries. It also highlights that his defensive play is a major red flag.
As for Staal, I think he’s a product of getting cushy zone starts because even though he carried the puck in over 70% of the time, he didn’t have a major role in the neutral zone and neither did Alexander Semin. Both of them were sheltered territorially and it wouldn’t surprise me if this limited the impact they had in terms of creating shots off entries. Semin was still able to stay above water because the team created more shots off his entries and carried the puck in at an extremely high rate when he was on the ice. It speaks well of his ability to back the defense up and make plays when entering the zone and I would be in favor of giving him some tougher assignments next season so that he can have more of an impact on zone entries. Staal & Skinner strike me as players who need to be sheltered whereas Semin probably doesn’t need it as much.
The team’s depth issues also show up in zone entries because the Hurricanes were able to carry the puck in more than 50% of the time only when three forwards were on the ice and only six out of 14 had a positive neutral zone Fenwick scores. The fact that Jordan Staal’s line composes 3/5ths of that is also a problem because while those three drove possession, it didn’t result in many goals because they were primarily doing it through dump-and-chase play and having more overall entries than their opponents. Riley Nash also falls under this category.
The defense has some of the same problems.
The defense corps’ neutral zone scores match up with possession fairly accurately. Both Sekera & Faulk struggled to prevent carry-ins, but they made up for it by producing enough offense on their own and limiting entries by the opposition. John-Michael Liles was surprisingly effective at defending the blue line and I guess playing alongside Ron Hainsey helped that, as he also stayed above water despite producing little offense. Liles could be in for a nice season if the Hurricanes keep this pairing together because he was very good defensively and effective at creating shots off carry-ins. He just rarely carried the puck in last year and I’d like to see this change because that’s one of the reasons they traded for him. So the top-four might be in better shape than some think.
The third pairing, unfortunately, was a disaster and it didn’t matter who was on it. Jay Harrison played the left side for most of the year and was brutal both at preventing carry-ins and entries all together. It’s one of the reasons why he posted one of the worst shot attempt differentials on the team and why the team’s third pairing was a mess. Pairing him with the swift-skating Ryan Murphy didn’t do much to help because even though Murphy was able to carry the puck in on his own at a high level, it didn’t raise the team’s average at all when he was on the ice and he also had trouble preventing carry-ins. Komisarek was a bit of a different breed because although he didn’t allow other teams to waltz in over the blue line with control of the puck, the Canes gave up a high number of entries when he was on the ice and ended up being a negative from that alone.
Defending entries is something that is also very important because if the goal is to carry the puck in more often than your opponents, then you might be able to get away with being a dump-and-chase team and forcing others to do the same by clogging the neutral zone & performing a roadblock at the blue line. We can get an idea of which players are good and bad at this through looking at on-ice entries against, but tracking which players were targeted on zone entries can give us a clearer picture.
Zone Entry Defense
Zone entry defense/targets are something I have been planning to track for awhile, but didn’t start until I read Tuisky’s piece on Five Thirty-Eight where he looked at this for the Flyers defense using information tracked by Jessica Schmidt. Unfortunately, I was in the middle of this project when I found out about this and decided to start tracking, so I don’t have any numbers on the Hurricanes aside from a few games late in the season. I will have about 60-65 games tracked of every other team at the end of this project and will publish it for free in a separate dataset.
Currently, I have about 20-25 games tracked of every other team from late-November to early-January and we can use this to see which defensemen do the best job at protecting their team’s blue line & preventing shots off entries in which their side of the ice is targeted. For this, we’re going to look at one great possession team (Los Angeles) and a terrible one (Calgary) to see how they differ in terms of defending entries.
Shots = Unblocked shot attempts
Los Angeles’ defense corps allowed a lot carry-ins than I expected during this time-span, but they did a very good job at limiting shots against. Drew Doughy & Alex Martinez were both very impressive in this regard. This data will be more useful once I get the rest of the season tracked and I can include forwards because LA is one of the best teams in the league at preventing controlled entries and this data suggest otherwise. Although, they rank much more favorably compared to Calgary.
Calgary had a very hard time at preventing carry-ins during this stretch and Butler & Russell in particular were awful at it. The Flames gave up fewer shots when Russell was targeted, though and their overall shots/target wasn’t awful when you consider how often they allowed carry-ins. Again, this is only 22 games, so it could mean nothing in the big picture, but it’s an interesting observation nonetheless. It could mean that Calgary’s problems are more related to how they entered the zone rather than how they defended.
Zone exits are another stat I have tracked for Hurricanes games over the last couple of years and I’ve changed my methods on how to track it since then. We all know zone exits are important because in order to generate controlled entries, you need to have speed through the neutral zone and this starts with exiting your own zone with control of the puck. Tracking how well teams do this has been a work in progress for me though because it’s a lot more complicated than it seems.
For those who don’t know, I track zone exits by logging how many times each player touched the puck in the defensive zone (while they were making an attempt to exit the zone), tracking whether or not they got the puck out and how they did it whether it was by carrying the puck out, passing it to a teammate in the neutral zone or by other means (banking off the boards or the glass, etc.). I also kept track of how many teams the player turned the puck over in the defensive zone and when they iced the puck. I usually look at a player’s “Success percentage” to see how good they were at leading zone exits, but ones done by carry or pass are logged as “exits with possession” and are more ideal than simply banking the puck out of the zone and having a teammate retrieve it.
Usually, I present exits in a table like this and will continue to do so for this project because it’s the method I started the season with, but I’m making some changes next year. The problem with just looking at success rates is that it treats all exit attempts as equal and a pass to a teammate within the zone gets tracked as a negative event when it probably shouldn’t. There’s also no indication of which players are just slamming the puck off the boards to get the puck out because those aren’t logged as “exits” unless a teammate retrieves it. Pressured exits are also treated the same as ones where there’s no forecheck. Therefore, I’m switching to a new system next year and will track more specific events on zone exits. Sort of like this:
There’s a good chance that the data might be the same, but I’m all for improving this system as much as possible.
Another thing I’m going to improve next year is how I chart scoring chances. There’s been enough studies to show that shot quality is hard to control at a team level and it probably isn’t repeatable. Team’s scoring chance differentials line up with their shot attempt differentials fairly well and there isn’t much to gain by looking at just on-ice scoring chances. I still think there is some value to tracking individual scoring chances, though and there might be something to gain by looking at how teams generate their chances. If a team is creating most of their chances on the rush as opposed to working a cycle or vice versa, then it might be easier for an opponent to prepare for them if it stays constant throughout the season. It would also be helpful to know where a player creates most of their chances and how they do it, so I think tracking individual chances & providing more information on how they were created can be useful.
If you’ve been following me on Twitter, you know that I’ve been playing around with this over the last few weeks and am hoping I can become quick enough to do it for the entire league once October rolls around. I’m still working out some bugs in the system and I’m not sure how to accurately log each chance type yet, so I’m open to your suggestions if you have any.
Conclusion/A Call to Arms
My goal with this is to provide better, more accurate data for everyone to use and I’m hoping I can get this book/dataset finished before the end of the summer. If you enjoy my work and are interested in helping me out, then consider visiting my donation page to pre-pay for a copy of my book to gain access to the data or donate some money so that I continue to do this & provide even more data in the future. I would release it for free, but tracking it requires a huge time & work commitment on my part, so I can’t do that at the moment. I’ve already received an overwhelming amount of support for this project over the last few months and I’m glad that so many people are already interested in this and I’m hoping it will lead to some great things for hockey analytics in the near future.