Do 'Expected' goals statistics suck?

[IWantSakicAsMyGM]

As a concept, I think we all agree that stats have limitations and should be taken with a grain of salt.

Where I differ from a lot of folks is that I feel analytics provoke an outsized reaction, particularly negative ones.

That's just my perception. In my time here, I've seen people be sanctimonious about analytics, and perhaps you're seeing an outsized reaction in that direction.

But again, I come back to this thread, which is "do analytics suck?" based on this random ass one game, and I would ask you, can you point me to any of the following thread topics?

-"Does this expert who had one bad take suck now? Should we disregard him entirely?"
-"My coach is moron. Does coaching suck? Are coaches useful?"
-"My friend watches the Flyers every night and his opinions are dumb. Is watching hockey pointless?"
-"I really thought the Red Wings played well, but the other team scored 4 more goals. Should we take the final score with a grain of salt?"

That all sounds dumb, right? That's exactly what "analytics produced this one result I didn't expect so do they suck entirely?" sounds like.

That's what "this shot should go in NINETY-SIX(!!!) percent of the time" sounds like. And I'm not trying to call out OP, but I mean c'mon, if you shot the puck off a pier, you wouldn't hit the water 96% of the time.

We don't have these very silly discussions about anything else being wrong.

I can understand where you're coming from. To me, it's sort like with streaming. When it first came out, it was a huge leap forward and was clearly better than what came before it. But then it grew into dozens of different services, each only providing one or two good things, and a lot of people no longer want to wade through all the trash to get the few treasures, and now have a negative reaction to the whole thing. Similarly, there are some analytics that are very useful for certain things, but there's also a lot of crap out there that is absolute trash, and much too time consuming to dig through and parse which is which.

Also, this thread is "do expected goal statistics suck?", not all analytics. And, suck might be harsh, but it's also true if the stats are being interpreted incorrectly. To answer the question in the OP about this specific shot, that shot is 0.16 xG because for all the shots taken from that location that fed into the xG numbers, about 1 in 6 have resulted in a goal. So, according to the xG model, that shot is expected to score about 1/6 of a goal, or 0.16 xG. But Danforth got off a much better shot than most of the ones feeding into the model, so the expectation for the average shot from that location don't match what actually happened, and wasn't really useful for predicting what happens in this one instance with this one player. Obviously, this isn't what xG is meant to predict, so anyone using it for this purpose is going to think it sucks.

 

[IWantSakicAsMyGM]

Individual game xg or any small sample size is pretty useless. Over a full season though, they will tell you who controls play. Now controlling play is important but it isn’t everything - shooting talent and goaltending matter too. It’s why Carolina basically leads the league in xgf% every year but get bounced when faced with teams that have similar , or even slightly worse numbers but better shooting talent. But , those saying advanced stats are useless don’t know what they’re talking about. For reference, these 4 teams were the best expected goals teams in the NHL last year. It matters quite a bit.

xG isn't really about controlling play, it's about taking shots from places that you're more likely to score, like in front of the net. In the playoffs, those are the areas that teams focus on shutting down even more, so it's harder to get those high percentage shots. Teams with better shooting talent can score from lower percentage areas that aren't as fiercely defended, which can give them the edge in results despite having lower expectations.

 

[FerrisRox]

It would be neither the first time nor the last time that someone in a profession admits to some guys with whom they're "shooting the breeze" admit that their entire profession and life's work is at least a little bit of bullshit (and for the record, I don't doubt you).

To be clear - maybe I mischaracterized what they were saying while condensing a three hour conversation into a paragraph - but they in no way thought that sports analytics were bullshit.

And, at least these two gentlemen, didn't think of themselves as "Hockey Analytics Guys" they thought of themselves as "Sports Analytics Guys." One of them, that very summer, was trying to get a job in baseball and apparently had a little traction for a role but ended up joining another hockey team instead.

What they were saying (one of them did 90 precent of the talking while the other just weighed in here or there) was that in the world of hockey, the analytics can't do what it does in other sports, which is "reveal" some kind of "hidden value" in some players.

They both agreed that what the analytics would show you is what you already knew. That guy you think is an excellent skater which great offensive instincts, great vision and a dynamite shot? Yup, he is all those things.

That defenseman that is a solid defensive defenseman but isn't very physical? The analytics show that he is solid in his own zone, but doesn't get many hits.

They weren't saying analytics were trash, nor did they disparage their line of work. What they said was they weren't unearthing any previously unknown information, they were merely echoing what was already known. They also both expressed that within their organizations, their department wasn't really involved in hockey decisions at all (though they did prepare reports on draft classes) and in one case, the guy expressed that his department was most useful for arbitration situations or new fuelling info for contract talks.

 

[Coffee]

Expected goals has always been a silly stat

How bout now? see the game ?