Putting Chicago’s Play In Perspective

Recently, after a loss to the Colorado Avalanche, I was about to tweet out a reassurance to Chicago Blackhawks fans that there was still time in the season to fix the problems that have plagued the team. I am usually a very optimistic and positive person so when it suddenly occurred to me that I had been handing out this same type of assurance since the start of the season I was forced to rethink what I was saying. I realized I was forming that moment’s reassurance based not upon anything objective, but upon my personal feelings about the team. Obviously, as a fan of the team, I always believe in them and have faith in them to do great things. As someone who analyzes the team from a systems and statistics perspective, I feel it is my responsibility to be realistic about how they are playing. That can be very had to do and I don’t blame people for not wanting to hear it sometimes.

Instead of tweeting reassurances, I went on a mini-rant about how I did not consider Chicago to be among the very best teams in the league given their play this season. This stirred up a little controversy of course. Many very smart hockey analysts disagreed with me citing Chicago’s good possession numbers. It is true, when you look at their numbers from a percentage standpoint, they look pretty good. Chicago has some terrific offensive talent that drives those numbers even when they have small slumps in shooting percentage that cause ripples of panic to radiate through the fan base. Frankly, I am not worried about Chicago’s offense. I expect any glaring outliers in terms of shooting percentage will likely correct themselves. My biggest concern this season has been with Chicago’s shot suppression numbers. Shot suppression comes from stifling the opponent’s ability to gain the offensive zone, creating turnovers and exiting the defensive zone cleanly and efficiently. This has been the backbone of Chicago’s success despite the widespread perception of the Blackhawks as a high end offensive team (they are that too of course). Since the beginning of the season, the shot suppression metrics were not favoring Chicago, but many thought that once the defense got sorted out things would improve. The defense has not been completely sorted out at this point of the season with just over 20 games left to play.

With all of this in mind, I went through the metrics from Chicago’s recent seasons to see how they compare to this season in detail. Using the current season’s averages in each metric, I calculated the deviation from those averages on a game by game basis. Because I started with the 2008-09 season and continued forward, there was a lot of information. To make it more digestible, I graphed out the deviation from this season’s average with a 5 game moving average.


0815 SV PCT 1415 DEV AVG

Chicago’s goaltending appears to have been far more consistent this season than in prior seasons with less variance in the highs and lows. Continue reading


Penalty Killing Metrics and Pitfalls in Evaluating Success

The strength of a team’s penalty killing, in my opinion, is more important than the strength of a team’s power play. The element of a penalty kill that is of foremost importance is the neutral zone forecheck of the shorthanded team. If the team with the man advantage cannot gain the attacking zone, they cannot take shots and score goals. Unfortunately, at this point at least, the microstats that detail the efficacy of a team’s neutral zone forecheck are not available to the public and it is debatable that all teams in the NHL even collect or use these types of stats. So, with the supremacy of the neutral zone forecheck in mind, what is most important to penalty killing that we can measure? We often hear that the goalie is a team’s best penalty killer and while that seems pretty logical, I thought I would look over the statistics for the past several seasons in the NHL to see which metrics best describe the success or failure of a team’s penalty kill.

I started out with a theory that the shot frequency would have an affect on how successful the penalty kill was over a longer term so I looked at a slew of different shot metrics. The trick with shot metrics on the penalty kill is that they come in such small sample sizes. Sometimes a PK lasts 10-20 seconds and the Power Play team scores on their first shot attempt. Other times, teams kill off 10 minutes of penalties in a game without giving up a goal. Either way, penalty kills are small portions of the game in terms of minutes, so the rate stats (CA60, FA60, etc…) we often use for 5 on 5 play can be heavily skewed.

I looked at FA60 (All Unblocked Shot Attempts Against Per 60), SA60 (Shots On Goal Against Per 60), SCA60 (Scoring Chances Against Per 60), GA60 (Goals Against Per 60), Sv% (Save Percentage) and PK% (Penalty Kill Percentage) from 2008-2009 through the present. I also used the raw numbers, i.e. Shots on Goal Against, Goals Against and the like, to see if I could find any correlation there as well.

The most obvious correlation in penalty killing metrics is between goals against and PK%.

 0815 GA60 PK PCT

Since a team’s penalty killing percentage (PK%) is based upon times shorthanded and goals given up, the 96.67% correlation between PK% and Goals Against/60 is, quite simply, expected.

0815 SV PCT GA60

A team’s Goals Against rate (GA60) also heavily correlates with the team’s Save Percentage (Sv%) on the PK. The correlation between GA60 and Sv% is less than GA60 and PK% because Sv% is based upon Shots On Goal and Goals. Teams give up a varying amount of Shots On Goal and have goalies with varying talent levels so while there is heavy correlation, this variance shows here.

0815 SOGA60 GA60

When we look at Shots On Goal Against rates (SA60) and GA60 from 2008-09 through the 2014-15 season, the variance due to the talent of the goalie becomes clearer. Teams with a higher SA60 tended to have a higher GA60 to the tune of a 20.21% correlation. This is still a fairly strong correlation from a statistical standpoint, but it really underlines the differences between teams in terms of the performance they get from their goaltending. Continue reading

Breaking Down Chicago’s Defensive Breakdowns

As the season creeps ever closer to the finish line, the Blackhawks have started a home stand that many thought would bring a nice points boost in the jam packed Central Division. After the first two games, Chicago had one point from a shootout loss against the Arizona Coyotes and a point from an overtime loss against the Vancouver Canucks. At the same time, the Nashville Predators and St. Louis Blues continued to gain points.

Chicago’s daily topic of conversation has revolved around the defense. Michael Rozsival and Johnny Oduya have come under heavy scrutiny all season, but at this point, fans have just had it with them. Both players have had rough seasons for Chicago and deserve some criticism to be sure, but Chicago’s problems go deeper than one bad defense pairing.


One of the most noticeable problems has been on zone exits. When trying to exit the defensive zone, the defenseman will often win the puck from the attacking team near the boards. At this point, it is time for a breakout play to move the puck up the ice. Virtually every breakout play used when the defense is under pressure in the defensive zone (i.e. not simply moving the puck back into the defensive zone to regroup with perhaps one forechecker pressuring) involves moving the puck up the boards to a waiting forward. There is usually too much pressure and congestion for a defenseman having just won the puck from the attacking team to simply skate the puck out of the zone. Trying this with heavy pressure often leads to turnovers and players being out of position to effectively execute their defensive zone assignments.

Once a defenseman has won the puck, he must quickly read his options and his defense partner must do the same. D1 is the defenseman with the puck and D2 is his partner. D2 will usually call out the breakout play so that D1 can quickly complete whatever maneuver he needs to make to begin the breakout. Whether the breakout is an Over, Wheel, Reverse, Rim, Up, etc…, the defense ends up moving the puck to a forward at or preferably, above the faceoff circle near the boards. This cuts down on the risk associated with making a cross ice pass with heavy pressure from the attacking players in the defensive zone. This also requires the defending forwards to keep a sharp eye out for what the defensemen are doing so that they can move to the correct position to receive the puck and break out of the zone.

Very often recently, Chicago’s forwards have not been ready to execute the breakout when the defensemen have retrieved the puck. You may have noticed recently when one of Chicago’s defenseman has gained possession of the puck and moved it up the boards where he expects one of the supporting forwards will be waiting, there is no one there but one of the point men for the opposition. The puck is held in the zone and the whole process starts over again. Not only is this sustained zone time problematic because it obviously leads to more shots against and chances for the opponent’s to score, but it has another effect as well. When there has been a board battle, particularly when it is below the faceoff circles or near the end boards, the defensive formation tends to collapse down toward the net creating a lot of congestion and traffic. The intention here is to put sticks and bodies in passing lanes near the net. This isolates the players in the board battle so that if the attacking player wins the puck, he has very limited options to move it to a better shooting area.

One way attacking players try to create shooting lanes when the defensive formation is compressed or collapsed down low in the zone is to move the puck back up high in the zone. This causes a lot of movement by the defensive players and provides an opportunity for the attacking players to find a lane to get a shot off. What has been happening to Chicago quite often is this: the defensemen win the puck low in the defensive zone, they move it up the boards where a forward should be waiting to carry on the breakout, no forward is present, the puck ends up on the stick of the opponent working the point, the defensive formation has to shift from low in the zone to high in the zone, passing or shooting lanes open up during this transition, the opponent is given the opportunity to get a better scoring chance. Essentially, the defense is doing the job of the attacking forward by moving the puck back to the point and decompressing the collapsed defensive formation because the forwards are not ready to execute their part of the breakout.

This is not entirely the forwards’ fault. The defensemen are well conditioned to execute these breakouts almost as a reflex. Quick decisions with the puck are a necessary skill of any NHL defenseman, but if the forwards are not ready to break out of the zone, blindly rimming the puck up the boards will not work. Just because a forward is pressured along the boards does not take away the forward as an option, so continuing the play and relying upon the forward to win the puck is not a bad plan.

Again, the big problem I have seen repeatedly in recent games has been the blind passes up the boards when no forward is present to battle for the puck. The additional problem with this is that when the defenseman looks to see if a forward ready to help and finds none, he has to decide what to do. That extra second or two holding the puck low in the zone is a recipe for disaster. Still under pressure from the attacking team, the defenseman must now either skate the puck to another location or find someone to pass it to. Standing there hesitating invites turnovers and poor decisions, so it is imperative that the forwards get to the right spot and that the defensemen make a quick decision for “plan B” to avoid these problems.


Another area of concern is combating the breakouts of the opponent. One of the Blackhawks biggest strengths last season was shot suppression. This season, shot suppression has been a real struggle for Chicago. One of the tools used very effectively last season was the neutral zone forecheck. Not only did the defensemen pressure the puck carrier trying to enter the offensive zone, but the forwards in the neutral zone did as well.

Chicago often uses a 1-2-2 formation with various motions therein to combat the opponent’s attack. One forward plays in the defensive zone to take away passing lanes and pressure the puck carrier to make a poor decision or force the puck carrier to pass into a specific area where other forecheckers are waiting to close off the routes into the offensive zone. This cuts down on controlled zone entries, which are known to lead to more shots against and offensive zone pressure.

At times this season, Chicago’s neutral zone forecheck has looked impressive and the efficacy of the system they use has shown in the stifling of their opponent’s zone entries. At other times, the system has been exploited by teams skilled in stretch passing or has outright broken down because of missed assignments, players being caught flat footed and sloppy play in the neutral zone.

I manually track Chicago’s zone entries and zone exits among other things. This data, often referred to as microstats, helps paint a picture of how effectively the team and their opponents are getting into the offensive zone and getting out of their own zone. Below, I have included data from 5 games in January of 2015 so that we can explore what this information tells us about how the team is performing. The games include Arizona (1/20/15), Pittsburgh (1/21/15), L.A. (1/28/15), Anaheim (1/30/15), and San Jose (1/31/15).

Below is a table of data from my tracking regarding Chicago’s defensemen. It is important to keep TOI (Time on Ice) in mind while looking at raw numbers. Players with more ice time will have higher numbers of course. The data in the chart directly below is during 5 on 5 play only. I track all situations, but this is the largest share of the data and most useful for our purposes here.

21415 table 1

 At 5 on 5, Niklas Hjalmarsson and Brent Seabrook played the most minutes during this stretch of games followed by Johnny Oduya, Michal Rozsival, Duncan Keith and David Rundblad. Hjalmarsson and Seabrook handled the lion’s share of faceoff duties in all three zones and particularly in the defensive zone. Rundblad was used very sparingly on faceoffs and then almost always out of the offensive zone. Hjalmarsson, Seabrook and Keith were paired with Oduya and Rozsival sporadically during games on a shift by shift basis, usually when Rundblad was not being used.

In order to make the data above more palatable, I have converted the values into percentages. The first table below breaks down each type of entry as a percentage of the player’s total entries against. So for example, of the 51 times (100%) that Keith was targeted on an opponent’s zone entry, 12 times the puck was carried in resulting in 23.5% of Keith’s entries against being Carry Ins.

21415 table 2
Rundblad had the lowest Carry In Against % of the defensemen, but also had the lowest number of targeted entries against because of his rather limited ice time. The thing that stands out the most here is Rozsival’s stat line. 43.1% of the time that he was targeted by the opposition as they entered the attacking zone, they were able to carry the puck in. As we know, carrying the puck into the zone historically produces more shot attempts than dumping the puck in and trying to get it back. The really interesting thing here is that in tracking this data, I also track whether a forward was able to assist in pressuring the entry through the neutral zone forecheck or aggressive backchecking.

21415 table 3

As you can see, the percentage of carry in entries against the defensemen occur largely when the defense does not have the assistance of any forwards through either the neutral zone forecheck or aggressive backchecking. These are often situations where the defensemen are forced into a retreating type of coverage to take away the center of the ice and wait for reinforcements in the defensive zone. If the defenseman gets too aggressive in pressuring the entry in this situation and fails in his endeavor, his defense partner will end up defending the play on his own. That is a risk that teams try to avoid obviously. This also shows that when a forward was able to help pressure the zone entry with the defenseman, for the most part, the opponent was not able to carry the puck into the zone and either the entry failed or became a dump and chase situation.

When we look at the percentages from a comparative perspective, i.e., of the six defensemen, what percentage of the total was each responsible for, we start to see a fairly clear picture of what happened during this 5 game span.

21415 table 4

39.1% of the carry in zone entries where a forward was there to help pressure the entry with the defenseman came against Rozsival. He also had the highest share of the carry in entries against him when no forwards were there to assist. The highest shares of the entries that failed with forwards assisting in pressuring the attacking players belong to Oduya, Keith and Rozsival.

When the defenseman was on his own to thwart the attacking player’s attempt to enter the zone with the puck on his stick or by passing it to a teammate, Seabrook had the highest share of successfully defending against the entry. Hjalmarsson was close behind him with Oduya in third. Keith was last in this category, but again he had the second lowest ice time and targets as well during this period of time.

When we split up the team total in each category of zone entry, we can see which defensemen were responsible:

21415 table 5

So, from this information, we know that during this recent span of time, Rozsival had the most obvious struggles keeping opponents from entering the attacking zone with control of the puck. Despite being 4th on the 5 on 5 TOI depth chart, he had the highest share of the controlled entries (carry/pass in entries) of the defensemen. Oduya had the highest share of pucks being dumped in against him, but also the highest share of those dump ins being successfully retrieved. Seabrook had the highest share of failed entries against or put another way, had the most success at denying the attacking player to get into the zone. Both Hjalmarsson and Oduya had impressive marks in this regard as well.

Once the attacking team gained the zone during these games, how did Chicago get the puck out? Zone exit data can help us explore this. I only know of a handful of people who track exit data and all of us seem to keep track of different things, so frankly it is tough getting any comparison data around the league to give a decent gauge here. The only thing we can really do at this point is compare Chicago’s players against each other with the understanding that particularly when it comes to forwards, the defensive formation and breakout formation being used at the time will influence who is carrying the puck out of the zone.

Below is a table showing which players were responsible for getting the puck out of the defensive zone. Many of these plays happened after other players forced turnovers, made good passes or got the puck to an area of the ice where a teammate could retrieve it so I have included those as well. They are broken down into controlled and uncontrolled actions. The controlled actions include passing in the zone, carrying the puck out of the zone and passing the puck out of the zone. The uncontrolled actions include tossing the puck to an area of the ice where a teammate is likely to retrieve it and dumping the puck out of the zone.

21415 table 6

As you can see, during this span of games and frankly all the time, the defensemen are largely responsible for moving the puck in the defensive zone.

21415 table 7

The table above shows the percentages for the touches by defensemen only. The more the puck can be moved while under control the better. Many of the actions I have labeled as “Dump Outs” are actually passes to players in the neutral zone that missed their mark and carried on into the attacking zone with forwards in pursuit. Others include simply shooting the puck out of the zone and causing the opposition to have to go back, retrieve the puck and regroup in their own defensive zone.

When passes into the neutral zone miss or the puck is dumped out and icing is called, this is considered an unsuccessful zone exit and is not included in the data above. Below is a table of turnovers in the defensive and neutral zone forced by Chicago players and committed by Chicago players. Again, the defensemen are largely responsible for getting the puck back from the attacking players and moving the puck in the defensive zone so it is expected that they would have higher numbers in these areas.

21415 table 8
For the defensemen, the passing turnovers are largely due to trying to move the puck to an area of the ice where the player believes one of his teammates will be waiting to receive it. This is particularly good evidence of the problems Chicago has had on breakout plays under heavy defensive zone pressure that I referenced at the beginning of this article. 74 of the 97 passing turnovers were committed by the defensemen. This also includes passes into the neutral zone from the defensive zone that went directly to the stick of an opposing player allowing the attacking team to immediately put the puck back in, i.e. failed zone exits.

Another troublesome indication from the table above is the lower number of turnovers forced by Oduya. While he may not have had the struggles Rozsival had on zone entries during this span of games, his inability to get the puck from the opponent allowed them to have more zone time. Another thing to keep in mind here is that often during this period of games, once play was stopped after the goalie made a save, Hjalmarsson and Seabrook were brought on to handle the defensive zone faceoff. This pairing has borne the brunt of the defensive lapses committed by their teammates as a result.

The recent call up of Kyle Cumiskey and the injury to Rozsival may alter the dynamics of the defense enough to stir up some changes in how the team is playing, but the systemic issues facing the team on zone exits will require a larger adjustment. It remains to be seen how long Rozsival will be out of the lineup, but if the defensive pairings show an improvement in their play without him, the right move will be to keep him out for a while longer. He is an older player with a history of injuries that have caused significant wear and tear and affected his skating. Rozsival has good instincts and still makes good plays, but it just seems that his age and mileage are catching up to him. He certainly tries to make the plays that made him a valuable defensive asset in the past, but simply cannot physically perform in the manner necessary to be as effective as he once was.