Explaining the Grabovski-Bozak "Stats" Debate in Shinny Hockey Terms

Blake Murphy
July 06 2013 09:22AM

First thing’s first: Mikhail Grabovski is an absolute gem. Whether or not you think it’s appropriate, you have to laugh at the crazy rant Grabo went on to Jonas Siegel after he was bought out on Thursday. Can’t say I blame him, or that he was wrong on any of those points.

There has been some discussion on Twitter and via articles as to whether Grabovski was a good player, a victim of circumstance and underappreciated or a guy blown up by #fancystats who just couldn't get the job done. It hasn’t been a back and forth so much as people restating their opinion over and over again, with analytically minded people (or people who watch the games at both ends of the ice) thinking this move is asinine and some main stream media people and Bozak fanboys supporting it. There are people in between those poles but those extremes yell the loudest.

Cam’s post sums the anti-buyout side nicely, while I think this picture sums up the other side:

But it really shouldn’t be a debate of analytics against the #watchtehgamez crowd. In fact, while some of the "advanced statistics" that have been cited are "advanced" in terms of access, calculation and name, they’re really based on very fundamental, practical and easy to understand ideas about the game of hockey. They’re ideas that anyone who has played the game or watched closely inherently knows, but once it’s quantified some people react negatively as a conditioned response to stats. 

So I wanted to take the time to go through some of the stats cited around Grabo (and Bozak, Bolland and Clarkson) and explain them in more simple terms. This isn’t meant to be a primer on the stats, and the analytically-inclined can probably gloss over this. This is an explanation for the people who think that numbers ≠ watching hockey and numbers ≠ the realities of the game.

Quality of Teammates

Here’s what I want you to do: go to the next session of shinny hockey you can find. After a few minutes, identify the best and worst players on your team.

Spend half the game manipulating your line changes so you’re only playing with the best player on your team. (As you'll see, this could be given the verb Bozaking.) At the halfway point of the session, change that strategy so you never play with him or her and instead play with some of the lesser players.

What do you think will happen? Well, if the teams are relatively even and not too subject to randomness, you’ll probably do a lot better with the good linemates than the bad ones. Unless you’re some sort of other-worldly player, the quality of your teammates will have an impact on how you perform.

This is the reason people measure Corsi QoT, or Quality of Teammates. Corsi QoT tells you what the average Corsi score (a measure of shot attempts for and against) of a player’s linemates was. Since the Leafs were a negative-Corsi team and thus everyone is likely to have “negative” teammates, we can use Corsi Rel QoT, which shows this same stat relative to the team average.

The table below shows that, while Grabovski had better teammates over a three-year stretch, Bozak had BY FAR better teammates this season. Phil Kessel probably has something to do with that.

Corsi QoT

  2010-13 2012-13 2012-13 Rel QoT
Grabovski -4.47 -15.709 -3.182
Bozak -6.19 -11.687 2.452

Quality of Competition

Now imagine that same shinny game where you’ve evaluated all the players quickly at the beginning. Instead of focusing on teammates, this time identify the best player on the opposing team.

Spend the first half of the game matching up with him and trying to shadow him – your job is to shut him down. For the second half of the game, manipulate your shifts so you play against the other team’s weakest line. Against the top line, you're focus is defensive and against the lesser line, you're free to gamble and play offensively because they are less likely to capitalize on mistakes or be able to stop you.

Like with the teammates example, you’re very likely to see a change in your performance based on these situations. This is the reason people measure Corsi QoC, or Quality of Competition. Corsi QoC tells you what the average Corsi score of a player’s opponents was. You can also use Corsi Rel QoC, which shows this same stat relative to the average player on opposing teams.

The table below shows that, while both players played against above-average competition overall, Grabovski has had a more difficult set of opponents.

Corsi QoC

  2010-2013 2012-13 2012-13 Rel QoC
Grabovski 1.17 2.509 1.457
Bozak 0.81 2.299 0.858

Shooting Percentage and Save Percentage

Let’s go back to our shinny example, but forget about QoC and QoT for the time being. Now imagine you’re out there and your team’s goalie is just brutal. Muffins from the point, unscreened, are finding their way in. The rebound control is terrible, so even if you do a good job defensively, your goalie is giving the opposing team second and third chances.

At the other end, your line has had a few bad bounces – a great save here, some iron there, you feather a great pass that an open man in the slot whiffs on. Just some bad puck luck for your line.

Add those two elements together, and it’s difficult to see your line coming out looking good. You didn’t do anything wrong, though. You made the opposition’s first shot a low-percentage one and you got good chances in the offensive zone. Would it really be fair to look at your negative plus-minus to evaluate you?

This is why people measure PDO, which adds together the team’s save percentage when a player is on the ice and the team’s shooting percentage when a player is on the ice. This has been shown to regress heavily over time (to a mark of 1000), such that few players can show a sustained impact on the shooting and save percentages of their team.

The table below shows that, while Grabovski was a bit luckier previously, Bozak was the benefactor of extremely positive variance this past year. The goalie’s performance when Bozak was on the ice was much better than when Grabo was – even if Bozak is the chilliest of bros, I doubt very much James Reimer and Ben Scrivens tried to be worse when he left the ice. Bozak’s plus-minus, if you want to look at that kind of thing, was also helped by a high shooting percentage by the team when he was on the ice (thanks, Phil!).

 

2010-13

2012-13

  Sh% Sv% PDO Sh% Sv% PDO
Grabovski 9.34 910 100 8.45 904 988
Bozak 8.73 906 993 11.01 917 1027

Zone Starts

This one is a little tougher to put into shinny terms because it’s unrealistic, but assume rec league hockey instead this time around. Now, you sit on the bench until there’s a defensive zone faceoff and then you’re sent out. Because we’re playing a league game now and not shinny, you can’t really take three minute shifts, so once your minute is up, you’re off. Your job, then, is to keep the puck out of the net and get the puck out of the zone and then get off the ice.

But for the second half of the game, the team decides you’ll only start in the offensive zone. You have one goal, and that’s to put the puck in the net. If the puck comes out of the zone in a safe way, hop off for a change.

It’s pretty easy to imagine what your scoring numbers might be like in one situation versus the other. That’s why people count Offensive Zone Starts and put it into percentage terms. A player who starts in the offensive zone 60% of the time with the goal of scoring is in a pretty good situation to put up points, while someone with a 40% mark has a tougher path to points and a greater defensive responsibility. 

The table below shows that Mikhail Grabovski has been deployed in the offensive zone far less often than Tyler Bozak, giving Bozak an easier path to points. That said, Bozak was still below a 50% mark due to his faceoff "prowess," which, even if it means little in aggregate terms over the course of a game, makes him a good candidate for important defensive zone daws.

Offensive Zone Start %
  2010-2013 2012-13
Grabovski 48.3 36.7
Bozak 49.5 44.8

Summary

So, put all of these things together now. You’re playing with some of your weaker teammates, you’re playing against the other team’s top line, you’re starting in your own zone most of the time, and your goalie is pulling a Toskala.

Do you really expect to put up good offensive numbers? Of course not.

And what about your teammate, a guy at the same position but one you’re pretty confident you’re better than. He’s playing with your best player against weaker competition and starting all his shifts in the offensive zone. The opposing goalie also lets in a pair of softies while he’s on the ice.

Is this guy better than you? Would you be okay with this conclusion? Of course not, you'd think it'd ridiculous for this guy to claim he's played better when a good chunk of his success is based entirely on his situation and some variance.

Well that’s exactly why Leafs fans are upset about Grabovski being bought out, especially since the end game turned out to be signing Bozak at a $4.2M cap hit (Grabo was at $5.5M with one year less).

This is not a matter of stats against non-stats – every single one of these “stats” cited to support Grabovski’s play are ones that were developed to measure things we’ve all experienced on the ice or, if not, can at least understand the frustration of. This isn’t reinventing the wheel, it’s just measuring the wheel that’s been in existence for some time in different vernacular.

So yes, as the table below shows, Bozak had a slightly better Relative Corsi and more points per 60 even strength minutes. But he did so with better teammates, easier competition, better puck luck, more offensive zone starts AND the benefit of passing to Phil Kessel (he actually scored less than Grabo). Grabovski is better than Bozak, and the Leafs made a mistake in waiving the former to sign the latter.

Grabo vs Bozak - 2012-13 Summary
  Rel QoT Rel QoC PDO Zone% G/60 Pts/60 Corsi Rel
Grabovski -3.18 1.46 988 36.7 0.86 1.14 1
Bozak 2.45 0.86 1027 44.8 0.62 1.51 4

080b400962217afff9510ac849d7e000
Blake is a news editor at The Score and also writes basketball for Raptors Republic and baseball at Fangraphs/Rotographs. As such, he doesn't write at TLN nearly as much as he should. Give him a follow @BlakeMurphyODC.
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#1 jasken
July 06 2013, 01:24PM
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Grabovski is a extremely talented forward you dont need advance stats to tell you that watch a hockey game. Grabovski being bought out had nothing to do with Bozak it had to do with how bad Leafs wanted Clarkson. Bozak could have signed for 3 mil right after Bolland was acquired and Grabovski would have been bought out for Clarkson. Does that mean oh they got Bolland to replace Grabovski no it means they basically traded Grabovski for Clarkson was this a mistake some will say yes others no I am still up in the air give me a few years of Clarkson then I will decide if the Leafs were smart to do it or not.

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#2 jasken
July 06 2013, 07:12PM
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Here's an better debate rather then your stats.

Coach says "I want you do this." Bozak does is without question, Grabovski says coach is stupid doesn't use me properly, doesn't talk to me, has no trust in me damn defence system.

End result 3rd line and 4th line for Grabovski. Others shaking their head.

Then you got Kadri over there snickering at the sideboards kidding with Lupul saying didn't I do that last year.

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#3 SkinnyFish
July 06 2013, 09:47AM
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That said, Bozak was still below a 50% mark due to his faceoff "prowess,"

Actually due to the Leafs being a terrible possession team and constantly being outshot and hemmed into their own zone far too often, only Orr and McLaren had an O-zone Start % greater than 49%.

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#4 leaferfan
July 06 2013, 09:56AM
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First I'm going to say people complain too much and focus on the negative. I do find value in advanced stats for pointing out the leafs shot differentials was terrible and changes needed to be made. This was a repeated mantra all season.

But no one wrote or proposed a credible plan with rigorous analysis to address it. For example, people would make comments like they need to add a checking center, or a shutdown dman or stop playing Orr. But no one could provide analysis by how much the leaf shot differential would improve if they sat Orr. Or added a 3C etc.

Just lots of post- event analysis of why it was a terrible move but not forethought and analysis of what to do.

Now I don't like the changes that Nonis made. But he made radical change because there were "holes" in the leafs game. Can you prove or show the changes he made will make the team worse and if so by how much?

Until you can show that, this sounds like people whining about Carlyle as a coach.

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#5 Badger M
July 06 2013, 11:58AM
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"The goalie’s performance when Bozak was on the ice was much better than when Grabo was – even if Bozak is the chilliest of bros, I doubt very much James Reimer and Ben Scrivens tried to be worse when he left the ice."

Hockey players are human beings, I mean, it's at least possible that Reimer feels more comfortable when he sees Bozak on the ice. If I was a goalie and one of my close friends say...gave me an approving nod after I made a nice save, it's certainly possible that I would feel more confident and play better.

I've started using and relying on #fancystats far more this offseason and I definitely agree with the main points of your article (screw Nonis for resigning Bozak and buying out Grabo), but in the end I side with Daniel Wagner's viewpoint on Corsi/Fenwick.

http://blogs.thescore.com/nhl/2013/03/12/why-advanced-statistics-approaches-hockey-completely-wrong-but-still-gets-things-right/

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#6 SkinnyFish
July 06 2013, 12:43PM
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What I will really miss with Grabovski gone is his boyish good looks, my partner runs Hockey Inside Out site..Come visit.

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#7 Badger M
July 06 2013, 12:44PM
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LMAO Go Habs Go!!

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#8 Mironovs Nose
July 06 2013, 01:26PM
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leaferfan - are you serious?

This site and others like it have been chock full of analysis about this stuff all year long.

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#9 Badger M
July 06 2013, 01:30PM
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Lol, I see Habs fans are trolling under our names! It wasn't us, I swear!

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#10 Jay
July 06 2013, 04:13PM
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jasken wrote:

Grabovski is a extremely talented forward you dont need advance stats to tell you that watch a hockey game. Grabovski being bought out had nothing to do with Bozak it had to do with how bad Leafs wanted Clarkson. Bozak could have signed for 3 mil right after Bolland was acquired and Grabovski would have been bought out for Clarkson. Does that mean oh they got Bolland to replace Grabovski no it means they basically traded Grabovski for Clarkson was this a mistake some will say yes others no I am still up in the air give me a few years of Clarkson then I will decide if the Leafs were smart to do it or not.

Your prose is atrocious. Try proofreading what you post if you want people to actually read it.

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#11 leaferfan
July 06 2013, 04:35PM
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@Mironovs Nose

Answering a question with a question. Well, yes I've seen plenty of shoddy analysis and strawman narratives.

But simply said, how much up or down will leaf Fenwick close change with the roster changes Nonis made?

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#12 jasken
July 06 2013, 05:39PM
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The only way for stats to work is if you put a person in another person's shoes. What would they have done with that person at that time in that moment. You cant you base stats on particular person in 1 split second of time with a particular group of people. If you could change that 1 person and say there is proof then sure.

This wont ever happen.. therefore noone really knows the difference, and outcome between 1 person and another they are only guesses, and speculation.

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#13 leaferfan
July 06 2013, 06:06PM
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If Anyone thinks Grabovski is a good player, no wonder we havent won Anything since 1967 1967 1967 1967 1967 1967 1967 When the Beatles were still young. He is Cute though

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#14 Doop
July 06 2013, 06:22PM
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I think it's clear that Dave Nonis has shown he's willing to do whatever it takes to draft Connor McDavid next year. Things are looking up Leafs Nation!

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#15 BCLeafFan
July 06 2013, 08:08PM
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Really enjoyed the article. Made me think of playing drop-in hockey with other old farts and having guys wait to sign in to be sure that: A. They'll be on the same team as a guy that actually knows how to play, or B. They won't be on the same team as a guy that's plain awful or a jerk, or the guy that invented the game and never tires of telling you all about it.... May I just reiterate my humble advice to all Leaf fans who are beyond stressed right now: "It's the summer time. Enjoy it. The games begin in the fall and that's when we'll find out what's what. You see, that's why they play the games." Go Leafs!

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#16 Dave
July 06 2013, 08:27PM
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leaferfan wrote:

If Anyone thinks Grabovski is a good player, no wonder we havent won Anything since 1967 1967 1967 1967 1967 1967 1967 When the Beatles were still young. He is Cute though

Well the post above illustrates why Grabo is a good player...

Also, would you happen to be James Tanner from PPP? You seem to show the same lack of intelligence he does?

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#17 Dave
July 06 2013, 08:39PM
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Also worth noting...

I believe Grabo is a vastly superior player to Bozak, but Carlyle would not play Grabo in the role he should have (top six center) for a variety of reasons (ineptitude, lack of intelligence, just didn't like him).

That being said, in a vacuum Grabovski's buyout makes sense because he was useless in a system where Carlyle refused to play him properly. After the Bolland trade, Carlyle saw no need to keep Grabovski and thus he was traded. Now the best solution would be to get a coach that, you know, plays his players properly, but buying out Grabovski makes sense if only because Carlyle is dumb and wouldn't have been used properly.

The Bozak signing is inexcusable though. No way he should be signed to that term and length.

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#18 Dave
July 06 2013, 10:22PM
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I think this makes sense, We Canadians spend money for our Hockey programs, different league, the kid gets good, maybe gets drafted by a Canadian based team, and is so good in free agency, he leaves for, of course An American team..Nice weather, less pressure and taxes, media not all ovwer you..No wonder they won the last 20 Stanley Cups.

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