March 2, 2013
A Closer Look
An Intro To Zone Exits

by Corey Sznajder

One thing that hockey statisticians aim to do is quantify different parts of the game so that we can have a better idea of what a team's strengths and weaknesses are. Shot-based metrics such as Corsi, Fenwick, and Scoring Chances give us an idea of which team is controlling the offensive zone, while zone entries tell us which teams and players are winning battle in the neutral zone. Both have been very helpful to advance the world of hockey analytics, but one thing that hasn't been looked at much is defensive zone play.

The argument could be made that it isn't necessary to look at defensive zone with shot-based metrics showing how many shot attempts a team is surrendering and how much time they are spending in their own zone. Likewise, zone entries help evaluate how effective a team is at advancing the puck while in the neutral zone and how it leads to them controlling play territorially. Why would we need to look at defensive zone play when we zone entry studies have pointed towards the importance of winning the battle in the neutral zone?

While neutral zone play is key, being able to get the puck out of your own end is also factors into a team's ability to drive the play forward. Defensemen face significant pressure handling the puck in their own end while setting up breakout attempts, which then leads to neutral zone play. Just going by my viewing experience, there are countless times where I have seen teams struggle to control even strength play because they simply can't get the puck out of their zone. They either have trouble beating the opponent's forecheck, or their defensemen are just so bad at handling the puck that it results in icing the puck or giving possession back to the other team.

I drew inspiration for tracking zone exits after reading a post by Derek Zona on how much the Edmonton Oilers relied on Jeff Petry to move the puck out of the zone. I explored this issue with the Carolina Hurricanes later in 2011-12 when newly-hired head coach Kirk Muller broke up the team's shutdown defense pairing because of Tim Gleason and Bryan Allen's struggles to exit the zone.

That's when I started tracking zone exits to see which teams and players are the most successful at leading breakouts, to show how effective certain players are at moving the puck forward and which players on each team are relied on the most to do so. Every team has players who are pegged as "puck-moving defensemen" because of their ability to create offense and work the power play, while others are labeled "shutdown defensemen" because of their defensive strengths and ability to stifle the opposing team's best forwards. Taking a closer look at zone exits can give us an idea of just how effective these "puck-moving defensemen" and how much they are relied on. Dave Tippett's quote about certain types of defensemen he coached sums up what I have been trying to accomplish by tracking zone exits:

"I'll give you an example. We had a player that was supposed to be a great, shutdown defenseman. He was supposedly the be-all, end-all of defensemen. But when you did a 10-game analysis of him, you found out he was defending all the time because he can't move the puck. Then we had another guy, who supposedly couldn't defend a lick. Well, he was defending only 20 percent of the time because he's making good plays out of our end. He may not be the strongest defender, but he's only doing it 20 percent of the time. So the equation works out better the other way. I ended up trading the other defenseman."

The process for tracking zone exits is fairly simple. I count every time a certain player touches the puck in the defensive zone while he is attempting to advance the puck forward, and note the number of times he was successfully able to do so. In addition, I track the puck was carried out, passed out, or moved out by another method, and also note if he turned the puck over or ended up icing it. Turnovers are tracked to show which players are doing more harm than good for their teams and more likely to be on-ice for goals and scoring chances against.

The first time I started tracking zone exits was for the 2012 Stanley Cup Finals between the Los Angeles Kings and New Jersey Devils. I discovered that one of the main reasons why the Kings were able to dominate the series was due to most of their top-players being able to exit the zone much more efficiently than the Devils. My tracking also showed which players on each team were being relied on the most to lead breakouts and displayed just how valuable Drew Doughty is to the Kings because of his ability to exit the zone cleanly without much issue.

This is a manual process that I have been doing during my down time (mostly during the lockout), so unfortunately, I only have around 200 games tracked from last season, which means there aren't many conclusions we can draw from my studies in regards to how much exiting the zone leads to driving the play forward. It is still a work in progress, but I should be able to reveal more once I get more games tracked last season and this season. However, I can show some of my observations so far and reveal which defensemen have exceeded and failed at exiting the zone cleanly.

For reference, the average success rate I had for defensemen in this study so far is 22.5%, so these 20 players have been well exceeding that limit. Most of them are conventionally considered good puck-movers, so there aren't many surprises here. That said, I didn't expect to see Toni Lydman, Mark Fayne, and Grant Clitsome to rank this highly, but they have been very good at exiting the zone in the games I have tracked. Clearly, it's not a surprise to see Ottawa's Erik Karlsson and Phoenix's Keith Yandle lead the pack here by a mile.

Let's take a look at which defensemen have been struggling to get the puck out of their zone.

The majority are defensive defensemen similar to what Tippett described, or third pairing guys who aren't being relied on to do much. The one exception here is Mark Giordano of the Calgary Flames. It is actually kind of surprising that he struggled so much to exit the zone because his offensive skill set isn't bad and he played considerable minutes on both Calgary's power play and penalty killing units. Again, this is still a very small sample in the grand scheme of things, so I'm interested to see how he looks once I have more games tracked.

As a side note, I should mention that any defenseman who fails to advance at least 10% of his breakout attempts is a member of what I am dubbing "The Gill Club." The chart above should tell you why.

I'll have more revealed about zone exits in the upcoming weeks once I get more games tracked, but I'm hoping this serves as a good introduction to the topic and hopefully sparks more people to join in. The more information tracked, the better, is what I always say. This is still a work in progress, but I'm hopeful that some new insights can be unveiled when taking a closer look at play exiting the defensive zone.