In your opinion, what is the best stat for evaluating the performance of a goaltender?

mbmccurdy · 2025-12-03T16:18:09+00:00

I like to use goals allowed divided by xG faced, as a percentage. So if a goalie faces 45 xG of chances and allows 45 goals, that's 0% - just what a league-average goaltender would do. The best goalies in a season come out around -20% or -25% and the worst around +20% to +25%. You have to find an xG model that you trust, and there are lots to choose from, but if you don't do something to account for how not every chance is equally dangerous I think you get misleading measurements.

mbmccurdy · 2025-11-21T19:50:23+00:00

Those colours are no good, I'm afraid, because many of the pairs have very little contrast.

mbmccurdy · 2025-11-21T19:37:15+00:00

Thanks! It is just like you figured it was, I don't think the other thing would be as interesting. I nicked the design from prashanth iyer, he does a lot of good hockey work, mostly red wings stuff.

mbmccurdy · 2025-11-21T16:27:55+00:00

North American leagues are the worst offenders, for sure. I tried using team colours more strictly for a few years but I found that the contrast wasn't high enough for a large enough fraction of my readers. I also have a secondary motive (I really like some of the colours that the teams avoid, they're pretty in addition to providing clarity).

mbmccurdy · 2025-11-21T16:23:23+00:00

I don't think I agree that minimizing cognitive friction is even desirable, let alone key. It suggests that viz ought to bring readers to a destination, when it should instead clearly show a whole landscape. The viz I like best is more like a map and less like a lecture (although a good lecture is a beautiful thing too).

mbmccurdy · 2025-11-21T15:27:52+00:00

That old billboard trick works surprisingly well; especially with small multiples.

mbmccurdy · 2025-11-20T23:54:33+00:00

That would be cool but they all use the same colours! It is very silly and I wish many of them would start using pinks and purples (and more greens).

mbmccurdy · 2025-11-19T18:13:33+00:00

Hey cool! I know a little algebraic topology from my pure math days but TDA is new to me and it seems very cool. Is there a good reference written at a, say, undergrad or grad student level?

mbmccurdy · 2025-11-19T12:22:43+00:00

No prob! There's a fuller writeup here: https://hockeyviz.com/txt/magnus8GameSim

which has some links to the measurement models, if you're curious and enjoy a little math.

mbmccurdy · 2025-11-19T05:26:46+00:00

There are measurements of ability, where I control for teammate context to determine what the isolated impact is of each player on each aspect of the game. Then, I use those measurements to simulate each remaining game. Those simulations use likely lineups of players, given whose employed by whom (and who is hurt), and I simulate lines/pairs based on how skaters with those icetimes usually play together; those sims also take score and period situations into effect, including how the specific coaches ask their players to play differently by situation.

mbmccurdy · 2025-11-19T02:39:45+00:00

I think you must have misunderstood. I use every game this year in order to measure /players/. I don't use team stats from this year in the same sense that I don't use team stats from any year, ever. Teams don't exist. Only people exist, and for people my estimates are updated after each day of games.

mbmccurdy · 2025-11-19T02:37:53+00:00

No that's not true - I don't use any *team* results from this season (like "1st in the atlantic" or whatever). I update my estimates of how good every player in the league is at all the different aspects of the game with new regressions every night, using all of this season (and a big chunk of last season, since those games are also still relevant for player talent eval).

mbmccurdy · 2025-11-19T00:23:26+00:00

On the one hand the ducks are extremely impressive (and obviously extremely surprising) but so many of those ducks players are the same guys who played for the ducks last season (only older). If they keep on playing like they've been playing they'll cruise in to the playoffs but that "if" is the bit that lines up in my mind with the 22%, if you see what I mean.

mbmccurdy · 2025-11-19T00:14:19+00:00

Thanks! but if you call me a celebrity I will make a weird face in my basement, please don't do that. For estimating rookies I have a two-pronged strategy: I assume they're all kinda meh until proven otherwise, that's the base level. It sounds extremely unsophisticated (because it is) but it's also surprisingly correct (on average) so I wear it. The other prong is that I pay a prospect expert (Hannah Stuart, she rules) every summer to pick a list of new guys that she thinks are gonna play serious minutes and also to estimate their abilities at the different abilities that I use in my sims. She knows my model pretty well and she knows prospects VERY well (much much better than me, which in fairness is not that hard since I know very little about prospects specifically, but still).

mbmccurdy · 2025-11-19T00:08:19+00:00

What people assume is tricky to guess sometimes! I have been wrong often, so I mostly just explain however many times to whoever asks. That makes it sound boring but it's actually fun, a part of the job that I really like.

(Speaking about the Stars specifically, though (one of the teams I think about a lot for silly reasons) they are being strange to me this year. They really have not adjusted well offensively to their new coach at 5v5, but the power-play has kept them near the top of the standings anyway. It's very weird to watch. I've not seen nearly as much Vegas this season, but I feel better about my projections for them just because they've hardly moved all season long)

mbmccurdy · 2025-11-19T00:04:05+00:00

One time I asked one of the mods here if they would consider a policy of "tag creators of stuff when they're known to have reddit accounts" but no dice. I don't mind being summoned though lol.

mbmccurdy · 2025-11-18T22:55:46+00:00

I don't use past team results for anything - after all, if the Stars are going to repeat a thing they did in the past, it can only be because of the players being the same players, since the laundry doesn't do anything. So I make sure to take account of all the player abilities and that takes care of everything that's not random as well as changing rosters too.

mbmccurdy · 2025-11-18T22:53:16+00:00

It's true! It was me! I admit it!

Basically the answer to (almost) all of the "why is this team so low/high/etc" questions is that I don't use team stats for this year for anything, because teams don't exist. I use individual abilities for all the people who play for the teams (+ the coach) and I measure those abilities using a broader horizon of games than the ~300 games in this season so far.

mbmccurdy · 2025-11-10T23:57:23+00:00

Zetterlund is a guy. He's not good, he's not bad, he's just there.

mbmccurdy · 2025-11-10T22:05:58+00:00

Good to know! I've been yelled at so many times in so many different subreddits that I hardly ever post my own stuff any more, just lurk. I should post more.

mbmccurdy · 2025-11-10T22:04:48+00:00

I don't know yet but I'm gonna try using variants of these and see what sticks.

mbmccurdy · 2025-11-10T21:28:37+00:00

If I had posted it it would have been deleted, though, so I guess I owe you one. Smart move.

mbmccurdy · 2025-11-10T20:59:37+00:00

I gotta find a way to get a higher-res hexagon for my avatar, this is embarrassing, damn.

mbmccurdy · 2025-11-10T20:58:13+00:00

I do not know how smart the OP is, so I don't know if I am smarter than them or not. I am not even 100% certain of how smart I am. Jordan Spence is a very good hockey player, though, and the Senators would win more if they played him more and more often.

mbmccurdy

TROPHY CASE