This is awesome. Cool discussion to have, popped open a beer as well. This is a long post (tried to cut the length but wasn't really able to), but lots of content aimed at the advanced stats noob, apologies in advance but I think it will be helpful (especially to the interested lurker, we know you are out there!!!
Also,
I selectively bolded some lines so easier to skip around in case you already know some of the info. Maybe not enough but at least it's something.
Anyway a couple of things (before we get to the question):
1) First of all these are really, REALLY bad team Corsi / Fenwick numbers. An absolutely average team will be 50% on both CF and FF percentage, if we look at our team it looks like our CF% is somewhere between 40 and 45% as a team? To
@XX this is one of those times it helps to see counts because otherwise you might disproportionally weight the three games that Timmins' and Jenik had when you're doing an eyeball estimate.
Or I guess you can look up what the team Corsi percentage is directly (turns out it is 42.8% at even strength which is... really bad). To put that in perspective, Bergeron will be a first ballot HOFer largely because of his 2-way play, Corsi / Fenwick are decent approximations of that. Bergeron's even strength CF% is 58.4... which is pretty close to the opposite of our team Corsi (100 - 42.8% = 57.2%). So
according to this widely-used and unbiased top level statistical approximation, our team is so bad at ES that the average of all our opponents' possession play this year is essentially the level of Patrice Bergeron.
I'm laughing as I type this because it aligns with the eye test -- and at least now we can quantify how bad our team is. This is one reason why playing with advanced stats can be fun, if used right you can discover some things.
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2a)
Regarding the definition of Corsi and Fenwick as statistics, Corsi measures all shot attempts when a player is on the ice - which includes shots on goal, missed shots, blocked shots - these all count as Corsi events. Computing the Corsi For % is what you'd expect, namely the number of events your team has divided by total events (when said player is on the ice). So if Chychrun is on the ice for 15 shot attempts taken and 10 shot attempts against, his Corsi For % for that game would be (15 / 25) 60%. Fenwick measures pretty similar things as Corsi, the only difference is that blocked shots do not count as Fenwick events.
Re: Fenwick, if Chychrun is on the ice for 15 shot attempts taken (but 5 shots are blocked) and 10 shots attempts allowed (and all 10 of those shots get through), his Fenwick For % for that game would be ((15 - 5 ) / (20)) or 50%. His CF% percentage would still be 60% because as stated above blocked shots count as Corsi events but not as Fenwick events. Aside from that one little difference, Corsi and Fenwick are designed to measure the same thing.
Higher numbers are better for both Corsi and Fenwick for percentages (CF%, FF% respectively), and the percentages vary quite a bit from game to game.
2b) Some ppl argue about which stat (Corsi or Fenwick) is a "better" indicator of what is happening in a game. To me, it doesn't really matter because the VAST majority of the time we're just looking for a high level summation anyway, and also in the vast majority of cases (easily 95%+), Fenwick and Corsi for percentages will be basically equivalent, esp over a whole season.
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But,
both Corsi or Fenwick have problems, esp if we have tunnel vision and don't consider overall context.
1) First, they're really dependent on quality of linemate and quality of competition. If I'm some bum and I play with GREAT linemates and defenders at ES, I'd expect to have relatively high Corsi / Fenwick numbers. Why? Because my linemates would be good at getting shots off (and through in the case of Corsi), and if my D don't allow any shot attempts against, I'll barely have any Corsi / Fenwick events meaning my CF% and FF% will be high. On the other hand, if my linemates are crap and I'm playing in the D-zone all game, of course I'm more likely to be in the ice for shot attempts so my Corsi / Fenwick would be lower. Same idea wrt whether I'm mostly playing against other teams' top six or bottom six.
2) Second, Corsi / Fenwick don't account for shot quality or shot location. As an example if I gain the blue line and immediately shoot (missing the net), and the puck is picked up by the opposition and they miss (or score on) a 2-1... well, according to Fenwick and Corsi that's one Corsi event for and one against, so CF% and FF% are both 50% which implies an even game. But that is obviously not what's happening, Corsi / Fenwick just measure the number of Corsi or Fenwick events, nothing to do with the quality of the events themselves. There are other stats which
do try to control for this sort of thing but Corsi and Fenwick do not.
3) Lastly there are other problems with Corsi / Fenwick that aren't immediately as obvious immediately but will skew the numbers. For instance if I'm a John Tortorella team and I'm 100% ok with giving up those point shots... well, when other teams take those shots, everyone's Corsi / Fenwick numbers will be worse because every shot counts as an event against. But if I have a coach that's always yelling, "SHOOT THE PUCK" then I'll probably have better Corsi / Fenwick numbers because more events for.
Specifically to this convo, what happens if I'm Chychrun this year and I'm deployed more often in the O-zone than the other Arizona D? Well, then I'd expect my Corsi / Fenwick numbers to be slightly higher than my teammates' because the coach is giving me more offensive opportunities. But what if Chych is spending lots of time against other players' top competition (which he is)...? Well, then I'd expect his Corsi / Fenwick to be slightly lower. The question is whether all these effects balance each other out... and honestly I have no idea. I'd want to play around with the numbers more before definitively saying one thing or the other.
Anyway there are quite a few factors that can influence the #s either way, that's why it's important to keep the big picture and use common sense when you look at stats.
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So now your question (finally!). How to analyze the table?
The first thing I noticed is how truly horrible our possession numbers are (see above), the second thing is for my own sake try to see whether anyone's Corsi / Fenwick are materially different. Like I expect, Fenwick and Corsi numbers are basically the same (assuming a decent sample size), no more than a percentage point or two difference for anybody (again
@XX this is another example where I'm glad I can see counts because it's obvious that Timmins, Jenik and Mayo didn't play much so I'm not even going to look into the difference between their Corsi / Fenwick, it's due to only a few events so almost certainly random chance).
And now
the Q -- is Chych our best player because he has one of the best CF% on our team. I would say... maaaybe. It's not clear because of those edge effects (#3 above). Chychrun is starting more in the O-zone than other Arizona D-men (that is what oZS% measures, we'll get to that later), but also he's averaging >3 shots a game which will juice his Corsi / Fenwick numbers a bit. That's not a bad thing Chychrun should be shooting (his shot is amazing!) but it means we should expect his Corsi / Fenwick numbers to be slightly higher. But, it looks like he plays most of his minutes against top competition (I looked this up to shut up some main board clowns), so that would lower his percentages. And he's putting up points which is good, also +11... but his Corsi / Fenwick percentages are below 50 so it's not like we're even close to dominating when he's on this ice.
And yes, a big part of that is probably our lack of offensive depth (after Keller / Schmaltz / arguably Crouse / Macelli there is a big dropoff) but it doesn't make it less true. But also his PDO of 105 is unsustainably high but not that surprising given a small sample size (PDO is a stat that is supposed to measure luck, it's not 100% accurate but 105 on our team is
extreme). We haven't discussed PDO yet but maybe we'll get there.
So for the reasons above, if I used advanced stats alone, I'm not sure Chychrun's our best player. He might be, but I don't think the answer is clear
just based on the stats. But, combine above average possession numbers (wrt other Yotes players) with the eye test as he continues to launch bombs and still amazing in transition... yes, Chychrun is our best player. That's why you need to use both the eye test and advanced stats.
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My other takeaway with the stats shown above -- I'm actually surprised at how good Valimaki looks based only on the numbers. Much worse deployment than Chych in terms of zone starts, but pretty much the same Corsi / Fenwick (ie possession) numbers. That's surprising to me (in a good way). Personally I'd want to look a little more into who Valimaki matches up against and also what he looks like in games before deciding anything, but based on the table you showed, I find Valimaki's numbers to be surprisingly good, so I'll pay more attention to him in the coming games and see what my eyes can tell me and if they back up these stats.
And THAT is another reason to get familiar with these types of stats. To change our expectations and maybe direct our focus in places it wasn't before.
Either way definitely worth the time needed to get smart about this stuff. Thanks again for starting the thread!