CJ Turtoro

I agree. But if we're just talking goalie, a couple of those shots weren't actually tough. Like the Barzal CHANCE was great, but the GOAL was on the totally wrong side of the net and Markstrom was so out of position it didn't matter.

Did it LOOK like it? IMO, yes. Did it FEEL like it? Definitely no. And I suspect most people would disagree with my answer to the first because of my answer to the second.

Good lord.

I say that in response to the results of this game. Not your non-zero-indexed, asymmetrically saturated color formatting.

Moneypuck had it as the largest by a pretty comfortable margin lol (they could only check games w/o a goalie change tho)

We wanted to hurt him

I think it's a little that he's Luke HUGHES and the understanding was that $9M may have been a bit of an overpay but it was a wink wink that we'd end up with Quinn so, fine.

Now it's a MASSIVE overpay, and Quinn is in Minnesota.

@evolvingwild.evolving-hockey.com can you run a query for me real quick? What is the largest gap in GSAx between teams in one game on record. Where does tonight's NJD-NYI match land?

This graph of yours went a bit viral over on the other place because it's objectively hilarious.

x.com/CJTDevil/sta...

Like this movement of shots to right up on the doorstep seems VERY likely to inflate xGs somewhat dramatically. And yes intuitive to me. Human trackers generally had a bias towards the middle of the OZ it seems.

bsky.app/profile/cjtd...

I think weighting shot types in general to historic averages is a worthy enterprise for estimating impact of automating shot type classification (some may push xGs lower, after all).

But we're talking a 10%+ overprediction on the twins' xG model this season. That's why I think warping is bigger.

I think ALL shot types definitely need a look, but based on those shooting percentages I'm not sure I think this is as big of a deal as the coordinate warping is.

A reasonable philosophical assumption, but my entry point to this issue was more empirical. I first noticed it in 2023 relative to the previous year so I never really considered that something could've changed BEFORE that. I suppose that may have just been lucky.

x.com/CJTDevil/sta...

How fundamentally differently does yours work? Ik the other models use like 3-4 different algorithms, but all use most of the same "training" data until now (except for Micah).

Oh oops, I thought it was from 2023-24 one. Oh well, apologies for mischaracterizing it in that thread. But regardless, yeah I think that that probably fixes MOST of the problem. This year seems to be not insubstantially worse than previous years too, and now your model has a few years headstart.

All good. I don't either, so it's been an education ~48 hours or so lol.

I agree. This is my full thoughts as it exists rn. I also give you your flowers as been the only site with which I'm familiar that correctly identified the warping and new shotdesignations as the principal issues with the overestimation.

threadreaderapp.com/thread/20078...

If someone more present on this site than me wants to recreate the thread. You have my permission lol. Just tag me in it.

Are you talking about the new shot designations now? That's kinda a different issue from the xG warping.

Apologies for everyone who is not on the other site, but I'm not rewriting the whole thread. Here are my thoughts on the state of the public NHL xG models.

threadreaderapp.com/thread/20078...

Certain shot locations were systematically over-recorded by humans and now that chips are doing it, there's been a drift. The drift has made some locations more/less dangerous than they seemed before. I'm describing this as "warping of xG fabric".

This is perhaps more illustrative. The low-slot shots were likely being incorrectly recorded by human trackers and the chips have correctly placed them as right in the crease. Small movement, hugh xG impact.

I just chose an arbitrary pre-tracking season as a control though, and it looks the way you'd expect. Interestingly their model always seems to underestimate the slot a bit, but it's definitely worse now.

Yes

I'm less convinced that those are of particular importance. It doesn't seem to offer any marginal improvement on the topic.

Decided to look more at this and these graphs are using @evolving-hockey.com's xG (because they have an excellent query tool that makes it easy).

So, while new shot designations are relevant, I think this graph screams that the true culprit was the warped xG fabric of the chip tracking.

Props to @hockeyanalysis.com for spotting that issue basically immediately and not letting his model drift into nonsensicality

Yeah so this says to me that, at minimum, we should think of these shot attempts fundamentally differently than other shot attempts. It's not unprecedented -- we already don't count blocks in xGs -- so we may as well bin these as something else. This is why private companies have several models.

Bah lol yup bsky.app/profile/cjtd...

How many xGs was that bad boy

Shots that don't make it to the net?

So on EH's model were under counting by 200/year from 2018-2022 and are overcounting by ~400/year since then with this year already being at 500.

So those new shots are big (bigger than I thought tbh) but definitely still a lot of impact from warping.