Last article, we looked at the most important position in hockey, the goaltender, and counted down the top 5 goalies today in the NHL. Today, let's take a look at defensemen, including both how to analyze defensemen and the top 5 in the game today
In the past few articles, I've tried to introduce some of the more important concepts in hockey analytics. So before we rank the top 5 teams, let's talk about how to analyze defensemen.
In the early days of the NHL, defensemen were responsible solely for preventing shots and keeping the puck out of their own net. However, as the game progressed, NHL defensemen soon expanded their influence by adding to the offensive side of the game. Bobby Orr was one of the early defensemen who revolutionized the position, showing that offense could come from the back end. Orr became famous for his offensive talent and contributions, as well as his highlight reel goals, including the game winning goal in the 1970 Stanley Cup to clinch the series for the Bruins.
And with the offensive revolution for D-men, players like Ray Bourque, Bobby Orr, and Paul Coffey, players with offensive and defensive skill, became the ideal defensemen.
Traditionally, people have used the plus/minus stat, which measures a players goal differential, hits, blocked shots, and takeaways, to evaluate defensive performance while using goals and points to evaluate offensive performance. If you've been following my previous posts or have some knowledge of hockey analytics, you'll know that some of those stats are less than ideal tools to measure players.
I talked in an earlier article about the importance of accounting for luck and randomness in player and team analysis. This is just as important when evaluating defensemen. Eric Tulsky wrote an excellent article about evaluating defensemen a while back. He looked at the repeatability of on ice save percentage for defensemen at even strength, finding that there was basically no repeatability in a defensemen's on ice save percentage in one three year sample to the next three years. In other words, defensemen don't seem to have much of an influence at all on his team's save percentage when they are on the ice.
This is an interesting (and perhaps contradictory) idea. What Eric is showing is that defensemen should not be given credit if their team has a high save percentage since they don't seem to be able to control that aspect of the game. As a result, to evaluate defensemen by plus/minus, which takes into account goals against, would be foolish, since the number of goals against a defensemen when he's out on the ice is highly influenced by the his on ice save percentage. The same problems occur at the offensive end. Defensemen have very little control of their own team's shooting percentage when on the ice, further weakening the case that plus/minus is a useful stat to measure defensive contributions or overall contributions.
But what about blocks, hits, and takeaways? Surely those are good measures of defensive performance, right? Well, not exactly.
There is one common theme for a player to accumulate a block, a hit, or a takeaway. His team must not have the puck. Obviously, having the puck is the sign of a good hockey team, so why should we measure teams or players based on the number of times a player does something without the puck?
Now hitting someone, blocking someone's shot, or getting a takeaway are all good things once the other team has the puck. You'd rather block a shot then have the puck reach the net and hitting an opponent with the puck can help your own team gain possession. However, unlike stats like Fenwick and Corsi, blocked shots, hits, and takeaways actually correlate better with losing than with winning. This is because those stats are indirectly measuring the amount of time a team does not have the puck. As a result, more often than not, it is better to have a low total number of blocks, hits, and takeaways, and teams like the Blackhawks, arguably the best team in the NHL, often have very low hit totals. Good teams have the puck too much to accumulate high hit, block, and takeaway totals.
This is why it is not great to use blocks, hits, and takeaways to evaluate performance of teams or players.
So what should we use? Shot attempt differential is probably our best bet. We can use a stat known as Corsi, which measures the differential of shots, missed shots, and blocked shots at even strength, to evaluate the overall performance of a player. Click here for a reminder of why we look at Corsi.
Corsi is not perfect by any means. Who you play with, who you play against, and how you are used can impact your Corsi in a game and throughout the season. We always have to account for context when looking at a stat like Corsi. However, Corsi is far superior to most stats that traditionally have been employed in evaluating players and defensemen.
Corsi is also a great stat because it takes into account both offensive and defensive performance. Dave Tippet, the coach of the Phoenix Coyotes, had a great quote in 2012 about this idea of how offense and defense are interrelated.
As Tippet points out, a player who excels on the offensive end can make up for weaknesses defensively if he helps his team keep possession of the puck. Meanwhile, a big hulking defensemen who is a so called "shut-down" defensemen can be a liability if he can't contribute to puck possession and offense.
Luckily, Corsi enables us to combine the offensive and defensive skills into one.
I'd quickly like to introduce a stat known as Corsi Relative, which is simply the shot attempt differential when a player is on the ice minus the shot differential when a player is off the ice. One problem with regular Corsi (known as Corsi on) is that a player on a bad team will look worse than a player of equal skill on a good team. This is because the second player plays with good players who also contribute to puck possession while the first player plays with worse players who don't do as well.
Corsi Relative is a handy stat that allows us to compare players from different teams on a more even playing field. Corsi Relative, or Corsi Rel as it is often called, can be used for both forwards and defensemen. It can be displayed via a rate stat (e.g. +10.4 /60 would mean plus 10.4 corsi attempts per 60 minutes of ice time at even strength) or via a percentage.
Another way we can look at Corsi is to look at what is known as WOWY, or with or without you. WOWY's, presented on David Johnson's tremendous stat site, displays a player's ice time and results with or without certain other players. By looking at WOWY's, we can get a better measure of which players are responsible for high (or low) corsi stats and which players are just riding off other's coattails.
Analysis via points and goals will probably never go away on the offensive side. While both are highly influenced by random fluctuations in shooting percentage year to year, talented offensive defensemen will contribute on the offensive end in the way of goals and points.
Zone exits are also a new stat that will undoubtedly be used in the future to evaluate defensemen. Unfortunately, there's not a ton of data on zone exits for most teams, and what we do have is still unprocessed at the moment. Further research still needs to be done before we can effectively use zone exits in evaluating defensemen and their puck moving abilities.
Looking at special teams performance is also important, but far more complex. For now, we will focus on even strength and leave power play and penalty kill evaluation for later.
So, we've done a quick overview on how to evaluate defensemen. Though there are ways to improve our analysis, we have covered the basic methods of evaluation. Using our new knowledge, let us rank the top 5 defensemen in the NHL today.
1. P.K. Subban
In the last couple of seasons, Subban has demonstrated again and again why he's the top defensemen in the NHL. Last season, Subban had a Corsi Rel of +13.7 and this season, a Corsi Rel of +16.7. This means that this year when Subban is on the ice, the Canadiens get 16.7 more Corsi events per 60 minutes than when Subban is off the ice. To give context, a Corsi Rel of 16.7 is the best among NHL defensemen who have played at least 20 games. Subban was close to a point per game pace and led defensemen in scoring last season, and while he has slowed down a bit this year, he still is 3rd in the NHL among defensemen scoring. Subban's With or Without You (WOWY) analysis shows a great player who carries his teammates possession wise.
2. Erik Karlsson
Like Subban, Karlsson has been one of the dominant defensemen in the NHL the past few years. Karlsson jumped onto the scene during the 2011-2012 season, scoring 19 goals and 78 points in 81 games. He had a Corsi Rel of 11.3. The lockout shortened season started strong for the 2011-2012 Norris Trophy Winner, with 14 points in 18 games. However, a gruesome injury cut short his 2012-2013 season. In those 18 games he had a Rel Corsi of over 20!!! This year, he has started strong again, leading NHL defensemen with 37 points and 10 goals in 39 games. His Corsi Rel has dropped slightly but is still very good at positive 7.9 Corsi Relative.
When looking at Karlsson's WOWY's in the past 3 years, no player who has played more than 15 minutes with Karlsson has a better Corsi For % when separate from Karlsson than Karlsson does separate from that teammate.
3. Dustin Byfuglien
Dustin Byfuglien may be made fun of about his weight, but there is no doubt that he is one of the elite defensemen in the NHL today. In 2011-2012, Byfuglien had a Rel Corsi of +13.1 per 60 and had 53 points in 66 games. In the lockout shortened season, Byfuglien had a Rel Corsi of +4.6 per 60. This season, Byfuglien has a Rel Corsi of +11.4 and is 3rd in NHL scoring among defensemen.
Byfuglien is one of the most underrated defensemen in the NHL and has in the past few seasons proven his critics wrong and shown himself to be one of the game's best defensemen.
4. Zdeno Chara
Chara is still thriving even into his mid 30s. His scoring has dropped off a bit recently, but his possession metrics are still going strong. In 2011-2012, his Rel Corsi was spectacular of +13. He dropped a little bit in the lockout season, but his Rel Corsi was still +6 playing tough defensive minutes. His Rel Corsi of +9.4 per 60 minutes this year is extremely impressive at age 36.
There is no doubt that Chara is nearing the end of his career, and yet, his recent performance shows that he still has some years to play as a top pair defensemen.
5. Kristopher Letang
Kris Letang has faced some injury problems in recent years, but when he's healthy, he's among the best defensemen in the National Hockey League.
Letang's lockout shortened season was extremely impressive. His 1.93 points per 60 minutes of play at even strength were the best among defensemen with at least 200 minutes of play. His Rel Corsi of +16.2 per 60 minutes was also fantastic. This year, his Corsi has dropped to only +3.4, though he has battled injury problems most of the year. A little more consistency from Letang and he would rise in the rankings, but there is little doubt Letang is among the NHL elite.
More from Bench Rider:
- NHL Power Rankings: Week of December 23rd
- Top 5 Goaltenders in the NHL (and How to Analyze Them)
- NHL Power Rankings: Week of December 5th
Pierce Cunneen is a hockey enthusiast from Philadelphia. Having grown up playing the game, he combined his two passions of data analysis and hockey to foster an interest in hockey analytics. You can follow him @pcunneen19 or contact him at firstname.lastname@example.org.