This week on Unconventional Wisdom we are going to take a step into the realm of the slightly more conventional fancy stats by looking at the Pittsburgh Penguins 2013-14 Play Usage Charts. However, just to shake things up and keep people on their toes I decided to look at not only the standard Corsi based Bubble Chart but also one that looks at Relative Plus/Minus. We've looked at Bubble Charts sporadically over the past few years, including one early this season. But it is worth having a quick refresher for those that do not recall what they represent.
The Player Usage Chart has an X-axis, the independent variable, based on Zone Starts. The value is derived by taking the number of Offensive Zone faceoffs divided by the sum of Offensive and Defensive Zone faceoffs. A value greater than 50% means the player is more often deployed in favorable offensive situations, which usually indicates some combination of favoring their offensive ability and trying to limit their defensive liability by giving them sheltered minutes. A value less that 50% means the player is more often used in tougher defensive roles, often because their limited offensive skill makes them better suited for being used to stop the opponent from scoring rather than trying to score themselves.
The size of the bubble on the chart will vary depending on what it is you are measuring, but most often people use it to look at Corsi or Corsi Relative. Corsi, if you have forgotten, is an on-ice team plus/minus statistic that is based on shot attempts rather than goals. You take the number of Goals, Shots on Goal, Missed Shots, and Shots Blocked that the player was on the ice for from his team per 60 minutes of ice time, whether he made the shot or not, and subtract the opponent's shot attempts per 60 minutes that occurred while the player was on the ice. To get Corsi Relative you also need to calculate the Corsi when the player is not on the ice, then you subtract the off-ice Corsi from the on-ice Corsi to get a comparative value which is supposed to show how the player performs relative to that of his teammates.
The same can be done with Fenwick, which is derived from shot attempts as well, but unlike Corsi it ignores Shots Blocked. Or in our case we are also going to be looking at a Plus/Minus based on Goals For and Against. The color of the bubble corresponds to whether it is a positive or negative value. On my chart the yellow bubbles are positive values while the white ones are negative. The size of the bubble is relative to the magnitude of the value. The larger the bubble the larger the number, positive or negative.
The Player Usage Chart uses a Y-axis, the dependent variable, based on Quality of Competition. This value varies depending on what you are trying to examine, although most often you see Corsi or Corsi Relative QoC. The Quality of Competition is a measure of the sum of Corsi or Corsi Relative of all opponents the player has played against, weighted by TOI. If looking at Corsi QoC it is only looking at the on-ice performance of the opponents, but Corsi Rel QoC looks at the comparative on-ice vs off-ice performance of the opponents. This can also be calculated for Fenwick and Fenwick Relative in the same way, although it seems to be very rarely used. The other charts we are looking at use the Goals based Plus/Minus QoC. A positive value indicates a higher quality of opponent, meaning the player tends to face off against some of the better offensive players. A negative value tends to indicate sheltered minutes, the player being held out except to be used against lower level opponents.
The chart is separated into 4 quadrants as the axes intersect at the 0 and 50% mark. The top right, Quadrant I, indicates players that are used in Two-Way roles, offensively minded individuals that get favorable offensive starts but can also match up against tougher opponents. The top left, Quadrant II, indicates players that are used in a Shutdown role, they have the toughest zone starts, more often having to break out of their own end, and they face off against the best players the opponent has to offer. The bottom left, Quadrant III, is referred to as "Less-Sheltered," individuals that tend to be defensively responsible enough to be given predominantly D-Zone starts but not entrusted to square off against the top offensive opponents, they are usually 4th liners. The bottom right, Quadrant IV, indicates Sheltered minutes, they get the most favorable offensive zone starts and face off against the lowest quality of competition, this is more often than not reserved for rookies and players that are considered defensive liabilities.
Corsi Relative Player Usage Chart
Plus/Minus Relative Player Usage Chart