Over the course of the season, I and others have often talked about the importance of defensive zone exits. On numerous occasions, we have debated (on Twitter) the pros and cons of simply getting the puck out of the zone to relieve offensive pressure versus starting a proper breakout play. People often argue that because players are tired at the end of a shift, particularly one where they have been actively defending for an extended period, simply getting the puck out of the zone without icing helps the team.
Ways the puck leaves the defensive zone:
- Happenstance: a pass from one offensive player to another misses and the puck ends up in the neutral zone causing the attacking team to regroup and restart their attack;
- Controlled Exit:
- Carry Out: One of the defending players gains control of the puck and skates it across the blue line;
- Exit Pass: One of the defending players gains control of the puck and makes a tape to tape pass to a teammate in the neutral zone;
- Uncontrolled Exit:
- Dump Out: One of the defending players gains control of the puck and shoots it into the neutral zone:
- Missing the intended target;
- Without an intended target, i.e. simply to get the puck out of the defensive zone;
- To execute a line change.
If the point of getting the puck out of the defensive zone is to go on the offensive attack, logically, an exit pass or carry out seems like the best plan to move the puck into the offensive zone. Dump outs have a high likelihood of going to a player on the opposing team. The defensemen for the attacking team are often back near the blue line and when a defending player gains possession of the puck, they usually start to back up into the neutral zone. This makes them the first players present in the area the puck is about to be dumped into by the defending player. Further, on lob types of dump outs, unless the defenseman is incredibly skilled at making that type of play while under heavy pressure, regaining possession of the puck is at best a toss up.
Even if the defending team needs to make a line change, dumping the puck out of the defensive zone is frequently not going to buy enough time to get the line change completed. We have all seen plays where a defending player dumps the puck out of the zone hoping to get it far enough to have time for a line change. Instead of getting through the neutral zone, the opposing team quickly gathers the puck and puts it back in the attacking zone. The line change may be completed for some of the forwards who are high in the zone, but often the defensemen, usually the same players dumping the puck out, cannot complete their change and must defend the attack while the forwards scurry to get in position on the ice.
Other similar situations include dumping the puck out of the zone and completing a full line change while the opposing team takes advantage of the far side boards being unoccupied to press their attack. Often, none of the players are able to get off of the ice on the line change and must continue to defend. Even when you consider that in some situations the point of getting the puck out of the defensive zone is not to go on the attack, but simply to execute a line change, carrying or passing the puck out still makes more sense. Anything that gets far enough to make the attacking team retreat and allow the line change to happen, also has a very real chance of going far enough for icing when this is attempted from the defensive zone.
Having a forward or defenseman control the puck at least until he reaches the opponent’s side of the red line and dumps it in is a far more successful plan for executing a line change. Obviously, there is always some risk involved in making line changes because hockey is a fluid game. Mastering when to make a line change and the way in which to do it is a difficult task, but players dump the puck out of the zone even when they are not trying to make a line change. Presumably, dumping the puck out of the zone is done to relieve the offensive pressure and with the hope that a teammate will recover it.
With this in mind, I took the data I tracked during the Nashville Predators versus Chicago Blackhawks playoff series and analyzed every series of events when the puck was moved out of the defensive zone to see what the results were from each type of zone exit. Sample size is something to keep in mind here of course, because this was during a 6 game playoff series between only 2 teams, but the exercise was interesting and perhaps a good place to start for a longer study.
I broke the zone exits into two categories: controlled (carry outs, exit passes) and uncontrolled (dump outs, icing). I then reviewed what happened during the next several tracked events to see whether the zone exit successfully relieved the offensive pressure and whether an offensive attack was pressed by the team exiting the zone.
Failed Zone Entries & Possession Change
Dump outs are recorded when a defenseman or forward on the defending team forces the puck out of the zone while breaking up a zone entry. I removed those types of plays from this analysis, because a failed zone entry was not exactly what I wanted to include. These plays are during transition with most of the players for both teams in or very close to the neutral zone thus creating more chaos and perhaps a better likelihood that a teammate of the player dumping the puck out will have an opportunity to recover it.
In going through that data, I found some trends worthy of note. While the information herein relates only to the Nashville versus Chicago playoff series at even strength, the trends may be similar throughout the league and serve as a jumping off point for further research.
A failed zone entry resulted in a zone entry attempt by the opponent, i.e. a change in possession, 71.12% of the time at even strength play. To illustrate, if a player from Team A failed in his attempt to carry the puck into the offensive zone, the following zone entry attempt was by a player from Team B about 71 times out of 100.
For Nashville, the percentage of failed attempts leading to a change in possession was 73.6%. For Chicago, the percentage of failed attempts leading to a change in possession was 67.9%.
Controlled versus Uncontrolled Defensive Zone Exits
Controlled zone exits, carrying the puck out or passing the puck to a teammate in the neutral zone, are preferred because the team moving the puck maintains possession. The push behind using shot based metrics in the NHL stems from these metrics offering a solid representation of puck possession. Puck possession has been shown time and again to be a strong predictor of team strength and success. Knowing that possession is one of the biggest keys for teams to succeed, it is logical that actions taken by the players to help maintain possession are preferable to actions that invite more opportunity for chance.
Uncontrolled zone exits, dumping the puck out of the defensive zone, happen quite frequently during a game and obviously in order to accomplish this, the defensive player must relinquish possession of the puck. Skill and practice can provide some correction for what otherwise would be luck to determine who gains possession, but giving up control is still giving up control.
Think of it like this, I fill my tea kettle with water and put it on the stove to heat up. As the water starts to boil, pressure builds up inside the kettle. If the pressure is not released, the kettle will simply explode. The spout and whistle allow some of the pressure to escape once it becomes too great to contain, but the water is still boiling. If I remove the kettle from the heat and pour the water into my cup, I can make tea. If I release a little of the steam and let the kettle cool for a few seconds, but then put it back over the flame, the pressure will build up again and I still won’t have a cup of tea.
Pressure in the defensive zone is much the same as a tea kettle. The attacking team brings the puck in and the pressure starts to build until either the attacking team scores (the kettle explodes) or the pressure is relieved. The defending player gaining possession of the puck can do one of two things: begin a controlled zone exit (take the kettle off of the flame and make a cup of tea) or dump the puck out of the zone (let the kettle cool for a few moments before putting it back over the flame).
My analogy presumes that dumping the puck out of the zone will lead to the puck being put back in the zone (i.e. the kettle being put back on the stove). It also requires that a controlled exit from the defensive zone will lead to an offensive attack by the exiting team. Hockey has forever had breakout plays that involve controlling the puck as you leave the defensive zone, so it is safe to say that these presumptions have long been a part of our collective hockey knowledge. In the age of data though, we can test this to see if the numbers support our assumptions.
Over the course of the Nashville versus Chicago series:
Controlled zone exits led to a zone entry attempt for the exiting team 88.27% of the time. So, if a player from Team A carried or accurately passed the puck out of the defensive zone, Team A had the next offensive zone entry attempt about 88 out of 100 times.
Dumping the puck out of the defensive zone resulted in an offensive zone entry attempt by the exiting team 28.73% of the time. Team A dumped the puck out of the defensive zone. Team A then had the next offensive zone entry attempt following the dump out about 29 out of every 100 times. 31.86% of these “successful” uncontrolled zone exits were the result of a forward on the exiting team forcing a turnover either in the neutral zone or in the offensive zone as the previously attacking team was regrouping to restart their offensive attack.
More simply put, of the 29 out of 100 of Team A’s dump outs that resulted in a zone entry attempt, 9 out of 100 were due to a player on Team A forcing a turnover in the neutral zone or the offensive zone while Team B regrouped for another offensive attack. This allows us to conclude that the team using an uncontrolled zone exit gained possession of the puck (without having to cause a turnover to do so) only 19.57% of the time. So, for every 100 of Team A’s uncontrolled zone exits, only 19 or 20 actually resulted in a member of Team A gaining possession right away.
The team dumping the puck out of the zone had to regroup, i.e. bring the puck back into the defensive zone and restart the breakout, on 13.75% of these “successful” uncontrolled zone exits. Considering that technically the breakout and subsequent offensive push resulted from a re-formed breakout instead of the original uncontrolled zone exit, we may want to consider excluding these from our figures. If we do that, the team dumping the puck out of the defensive zone was responsible for the next zone entry attempt only 25.79% of the time or 26 times out of every 100. Excluding the regroups pushes the percentage of successful uncontrolled zone exits brought about by a player forcing a turnover up to 36.96% (or 9.6 of the 26 successful zone exit attempts).
Dumping the puck out of the defensive zone resulted in an offensive zone entry attempt by the opponent 71.27% of the time. Team A dumped the puck out of the defensive zone. Team B then had the next offensive zone entry attempt following the dump out about 71 out of every 100 times. If we exclude the times in which the exiting team went back and regrouped, this percentage goes up to 74.21%.
Of the uncontrolled exits that resulted in the exiting team attempting the next zone entry, 85% of those entry attempts successfully gained the zone while 15% failed to do so. Of the uncontrolled exits that resulted in the exiting team’s opponent attempting the next zone entry, 88.66% of those entry attempts successfully gained the zone while only 11.34% failed.
Team A dumps the puck out of the zone 100 times.
Team A attempts the next offensive zone entry 26 times. Team A successfully enters the offensive zone 22 times and fails to do so 4 times. 9-10 of Team A’s successful zone entries are the result of a player on Team A forcing a turnover.
Team B attempts the next offensive zone entry 74 times. Team B successfully enters the offensive zone about 65-66 times and fails to do so about 8 times.
Essentially, whenever one of the teams dumped the puck out of the zone they had a much greater likelihood to be defending against an offensive attack than pressing their own. When paired with zone exit data by team and player, it is easier to identify strengths and weaknesses in the systems used and the players. The higher the player’s number of uncontrolled exits from the defensive zone, the more likely the player is either forced to defend the opponent’s attack immediately following his uncontrolled exit or get off the ice and leave his teammates to defend the attack.
The successful uncontrolled zone exits, i.e. the dump outs that worked, as noted above, were few and far between, accounting for only 25.79% of the uncontrolled zone exits with the remaining percentage winding up back in the defending team’s zone. To see the type of impact these unsuccessful attempts at clearing the zone had, I went through the even strength data from the Nashville versus Chicago series and did the following:
- identified the team’s first attempt to clear the zone by using an uncontrolled exit;
- noted the type of zone exit that was eventually successful for the team;
- the number of distinct periods of possession for the attacking team;
- the number of exit attempts before the defending team was able to attempt an offensive zone entry;
- the amount of time that elapsed from the first dump out attempt until the successful zone exit.
*It is important to remember that I considered a zone exit successful only when the exiting team was able to attempt the next offensive zone entry or the sustained offensive pressure by the attacking team was put to an end.
Impact of Unsuccessful Uncontrolled Zone Exits
The type of successful zone exit eventually used by the defending team:
- Controlled (Carry out or Tape to Tape Pass) 69.38%
- Uncontrolled (Dump Out without the necessity of a turnover being forced by the defending team in the neutral or offensive zone) 14.34%
- Uncontrolled with Turnover Forced by Defending Team (in the neutral zone or offensive zone) 8.91%
The remaining periods of sustained offensive pressure after the defending team tried to clear the zone with an unsuccessful uncontrolled exit ended as a result of:
- End of a period of play 1.55%
- Committing a penalty (PK) 1.55%
- Drawing a penalty (PP) 1.16%
- Goal by the attacking team 4.65%
The team was forced to continue defending against the offensive pressure when an uncontrolled zone exit attempt was unsuccessful for an average of 2.42 distinct periods of possession by the attacking team. The time that elapsed after the initial unsuccessful uncontrolled zone exit attempt (Additional Time Defending) averaged out to 26 seconds.
The 26 seconds was of course in addition to the time the team had already been defending against the offensive attack prior to trying to dump the puck out of the zone. That may not seem like much, but in “defensive shift” time, 26 seconds on top of what a player has already skated can be an eternity. The Additional Defending Time ranged anywhere from 4 seconds (0:04) to over 2 and a half minutes (2:32). The distinct periods of possession for the attacking team ranged from 2 up to 6 with between 2 and 6 attempts to clear the zone during those possessions.
The periods of sustained offensive pressure that ended in goals averaged 2.58 distinct periods of possession and Additional Defending Time of 26 seconds. 12 of the even strength goals scored during the Nashville versus Chicago playoff series came when the attacking team was able to sustain offensive pressure due to unsuccessful uncontrolled zone exit attempts.
Many of the dump out attempts came after turnovers in the defensive zone, whether directly off of a defending player’s stick or due to poor passes. They also occurred after players simply swatted the puck to an area such as when trying to clear the front of the net. These types of events often make players scramble and the temptation to simply dump the puck out of the zone becomes very strong.
Tracking whether the puck was dumped out of the zone after uncontrolled defensive zone touches (tossing the puck to the corner to clear the goalmouth, etc…), passing turnovers and turnovers directly off of the stick can give insight into how defensive pairings and line combinations are working. This can also give us information on how defensive systems and breakout systems are working, such as which players should be the first pass option or second pass option, which players tend to make poor decisions with the puck under heavy pressure and more.
These details are important despite seeming like such a small part of the game. The impact they have upon the course of events during a game is very real. Again, while this data is limited to a playoff series and thus equipped with all of the pitfalls of a small sample size, it seems to support the long held beliefs of many smart hockey people in that it shows that controlled actions and possession are far more effective than leaving things up to chance.