Wednesday 28 December 2016

Explainer

What are Man-Games Lost?
Man-games lost (MGL) to injury is normally understood to be the total number of times a team has had a player or players unavailable to dress for a game, i.e. a single player missing 10 games builds up 10 MGL; 2 players each missing 5 games also builds up 10 MGL.

MGL is the injury statistic most commonly referred to the media and figures are recorded and published in some form on a pseudo-official basis by the vast majority of NHL teams. However...

What are the drawbacks?
Teams' "official" MGL figures are not published on an aggregated basis by the league, nor is there necessarily any consistency in how teams compile and record the figures.

For example, some teams count "retired" players still under contract (more on this later), some count non-NHLers who are injured at the start of the season and can't be re-assigned until healthy, some have very hazy distinctions between healthy and injured scratches.

The most obvious drawback of using raw MGL figures is that they do not account for differences in value of the absent players. A game missed by Sidney Crosby of the Penguins is indistinguishable from a game missed by Gord Facepuncher of the Oilers.

What is CHIP?
Using a player’s cap hit to weight MGL is one way to approximate value.

Cap Hit of Injured Players (CHIP) represents the per-game cap charge of a player missing a game through injury/illness, i.e. annual cap charge* divided by 82.

(*Strictly, I use Average Annual Value (AAV) here, which includes the full amount of potential performance bonuses.)

Clearly, this is not perfect as a measure of value by any means - it won't take you long to think of examples of bloated UFA deals for ageing players or young bargains still on entry-level contracts (even allowing for inclusion of performance bonuses). However, cap hit is simple, stable, comparable across positions and lends itself to snappy, food-based acronyms.

Cap hit above replacement level would arguably be an easy improvement, but again, the focus here is on simplicity.

Why not weight by something else?
I often do - posts on my Twitter feed regularly include an alternative weighting by time-on-ice (TOI) and by Evolving Hockey's Wins above Replacement (WAR) metric, and some of the viz here also reflect the latter. However, it's impractical to keep updating all the viz here on multiple bases (and other weightings have their own drawbacks - less intuitive, messed up by small/zero samples, less stable over the season and, for TOI at least, less comparable across positions).

I'm definitely not claiming CHIP to be infallible or superior to alternatives, but it's a solid starting point that doesn't need detailed explanation.

Which players are included/excluded in your figures?
Players still under contract but either officially “retired” or out indefinitely with no prospect of a return in future are generally excluded from the figures from the start of the season (though remain separately identifiable in team charts).

Minor league players who are often put on Season Opening IR (non-roster) are excluded, as they simply cant be reassigned until cleared to play and (almost always) aren't likely roster candidates at that time. However, anyone who gets injured while on the active roster during the season is included.

Absences due to illness are included, but healthy scratches, suspensions, and absences due to entering the Personal Assistance Program or due to “personal reasons” are excluded.

Some subjectivity in all of this, especially where a player is in the Personal Assistance Program or where an absence officially described as being due to "personal reasons" is due to treating a mental health condition, for example, but I try to be consistent.

In 2020/21 and 2021/22, all Covid-related absences while a roster player (or expected to be) unless specifically understood to be due to visa issues have been included in the figures, though these won't necessarily align with the periods players were on the official protocol list. Injuries to players on the taxi squad rather than the active roster have not been included.

Do you record every injury to every player?
Not that simple, unfortunately. While the player records will be fairly comprehensive in most cases, a few reasons they won't be in others:
  • Injuries that don't cause any missed games (e.g. during the offseason) aren't covered
  • Playoff games missed are covered in separate summaries but are now included in the full player listings
  • Injuries while not in the NHL (or while on the taxi squad in 2020/21 and part of 2021/22) are excluded
  • My player records only go back as far as 2000/01

My team is always the most injured, right?
Yes.

How frequently do you update the figures?
Usually weekly, life-permitting. Fastest updates will by through the Twitter feed (@NHLInjuryViz) - normally done on a Sunday. Viz on this site might typically take a day or two longer to be refreshed.

Where is your data from?

Can you share your raw data?
Yes. Just ask nicely via @NHLInjuryViz and something can normally be arranged.