Tangotiger Blog

Tuesday, October 24, 2023

NHL Edge - Player Tracking

The NHL released their summary reports based on player tracking.  You can read about it in a few places.  Here's one from The Athletic.  

As this is the first version, I temper my expectations to the reality that we are dealing with production data in a production environment as a first release.  Sports, unlike all other products and services, really has almost no full testing environment available.  Whatever preparations we may get from putting tracking at one park (Salt River Fields) for a few weeks really is a drop in the bucket when you compare to the 30 parks x 81 games that millions are watching live, that an MLB season offers.  Things that you might not even know to test for manifests itself almost immediately in a live game.

So, I look at the first release of anything sports-related as if it's batting practice, but that everyone treats as a live game.  While we may all think we should be like Tim Raines on May 2, 1987, that's not reality.

Now, let's talk about player speed and MPH.  First I should point out that I am in the minority here because I am dealing with Inertial Reasoning when it comes to speed.  Whether MPH or KPH, speed is being represented like this.  When you throw a ball and you are trying to outrace a motorcycle, sure, that seems reasonable.  But life would be easier had we presented "time to plate" as the goto number.  See, when you present things in MPH, there's nothing more you can do with that.  It's the end-of-the-line. If you want to USE that number, that speed in MPH, the very very first thing you have to do is convert it to feet per second (or meters or yards).  But the key point is that the denominator is seconds not hours.

Why is that?  Because then you can actually use that number.  Suppose for example I tell you a runner is rounding third at full steam, at 30 feet per second.  How long until he reaches home plate?  That's 90/30 or 3 seconds.  And suppose an outfielder is releasing a ball at that very instant, he is 250 feet away, and the average flight speed for his throw is 100 feet per second: how long will that ball take to reach the catcher?  That's 250/100 or 2.5 seconds.  That's the story.  The runner will get to home in 3 seconds, the ball will reach home plate area in 2.5 seconds.  The catcher has 0.5 seconds to do something, whether to stand there waiting for the runner on a perfect throw, or he needs to scramble to get home on an offline throw.

An outfielder misses catching a ball by 3 feet.  How much faster would be need to be to catch it?  Well, if he was running at full speed for 2 seconds and 57 feet (28.5 feet per second) then he'd need to bump that up to 60 feet in 2 seconds (30 feet per second).  I could go on, and have gone on.  The point is simply this: make the number usable, applicable to the task at hand.  And the task at hand is not to just "present a number".  It's to give that number relevance, to let it resonate for the play.

Now to hockey: they are showing MPH, which of course is the default position.  But suppose I tell you that Connor McDavid is skating at 30 feet per second toward the net, and in the meantime, Cale Makar is defending him by skating backwards at 20 feet per second.  If I just gave you nightmares from school about two trains colliding, this is exactly correct.  This nightmare for you is a dream for me.  I've been waiting for this data all my life.  If McDavid is going to skate for 2 seconds at this speed, he will cover 60 feet of ice.  Makar in the meantime will cover 40 feet of ice in the same 2 seconds.  In order for McDavid to not beat him, one on one, Makar has to have 20 feet of space between him and McDavid.  (All numbers for illustration purposes only.)

There's a reason that we don't report 100m runners and 200m runners in terms of MPH.  It's not relevant, and it won't resonate.  What they do instead is report split times, like from 70m to 80m, they run in 0.98 seconds or something.  This is something that matters, because it gives them a real target to their overall 100m run.  Shaving 0.02 seconds in that split means shaving 0.02 seconds on their overall number.

It's an eventuality that the presentation of player moving speed (running, skating) will be in a form of feet or yards or metres per second.  Ideally, we can set the standard from the outset, rather than needing to reset it after a long battle.