# Updated WOWY analysis of Phil Kessel and Tyler Bozak

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### In my first post here at MLHS, I wrote an introduction to advanced statistics which generated some good discussion in the comments. A number of the comments were with respect to WOWY analysis and some more specifically with respect to Kessel and Bozak.  I will delve into that more here in my second post.

As explained in my introduction to advanced statistics post, WOWY is short for “With Or Without You” and looks at how the team performs when two players are on the ice together and when they are each playing apart from each other. So, for Phil Kessel and Tyler Bozak, we would look at how the team performs in three situations:

1. Both Kessel and Bozak are on the ice together
2. Only Kessel is on the ice
3. Only Bozak is on the ice

This table shows how the Leafs have performed in these three situations according to CF% (corsi for percentage, or percentage of shot attempts for and against that the Leafs took), GF% (goals for percentage, or percentage of goals for and against that the Leafs scored) and GF20 (goals for per 20 minutes of play). I included GF20 individually because I wanted to show how Bozak impacts the teams offensive production more specifically when Bozak is on the ice.

## Kessel + Bozak WOWY

A WOWY comparison of Kessel and Bozak
Stat2010-112011-122012-132013-144-year
Kessel with BozakCF%46.5%48.8%46.9%44.6%46.7%
Kessel without BozakCF%47.1%50.7%43.0%43.6%46.3%
Bozak without KesselCF%48.2%39.2%25.5%28.5%40.2%
Kessel with BozakGF%42.5%47.7%51.7%56.2%49.7%
Kessel without BozakGF%56.3%48.9%64.3%46.2%49.2%
Bozak without KesselGF%22.7%38.9%75.0%25.0%32.1%
Kessel with BozakGF200.730.930.971.190.95
Kessel without BozakGF200.901.151.400.720.98
Bozak without KesselGF200.370.881.000.670.62

Tables are good, but charts are often easier to quickly draw conclusions from. Here are WOWY charts for CF% and GF%:

Let’s start with the first chart looking at CF%, which can act as a proxy for puck possession but specifically measures which team is getting the most shot attempts. Anything over 50% means your team is getting more shot attempts than they are giving up; that is generally a good thing. As you can see, the lines for Kessel with Bozak and Kessel without Bozak are almost identical, indicating that Bozak had very little impact on Kessel’s overall statistics. Conversely, when Bozak is apart from Kessel, Bozak’s CF% stats tank, meaning Kessel (along with Lupul/JVR) has a significant positive impact on Bozak’s statistics. This would indicate that Kessel is not dependent on Bozak whereas Bozak is definitely more dependent on Kessel.

When looking at GF%, though, we see that until last season Kessel had a better GF% apart from Bozak than with Bozak. This reversed last season, when Kessel was better with Bozak than without. Over the past 4 years combined, Kessel’s GF% with Bozak and without Bozak is almost identical, which is consistent with what we saw with CF%.

Remember that sample sizes are significantly smaller when dealing with goals than shot attempts. There is much more fluctuation and randomness in these statistics, so we are more looking for trends than absolute numbers. This small sample size is a big reason for Bozak’s good GF% away from Kessel in 2012-13. In that season, Bozak only played just under 60 minutes of ice time apart from Kessel and in that ice time he was on the ice for 3 goals for and 1 goal against for a GF% of 75%. That isn’t anywhere close to a large enough sample size to draw any conclusions from. The overall trend we see in both the CF% and GF% charts are that Bozak has little or no effect on Kessel’s overall on-ice stats.

I wanted to look at GF20 specifically to see if Bozak is having an effect offensively or defensively on Kessel’s statistics. Here is how Bozak and Kessel’s GF20 WOWY chart looks.

For three straight seasons (2010-11, 2011-12 and 2012-13), Kessel had a higher goals for rate without Bozak than with Bozak but that reversed last season when Kessel’s had a better GF20 with Bozak than without. One season does not make a trend, though, and until last season the offensive production of the Leafs was significantly worse when Kessel was with Bozak than when Kessel was not with Bozak. Did something change last season? Has Bozak figured something out that has reversed the trend? We’ll have to see what next season brings. I suspect it was just an anomaly, but I’ll leave it up to Bozak to prove otherwise.

Now, we have to keep some perspective on these “without you” statistics for both Kessel and Bozak. When Kessel isn’t playing with Bozak he has mostly been playing with Grabovski or Kadri, both pretty solid centers so it makes it easier to maintain his “without Bozak” numbers. That said, Kessel has generally been as good or better with those other two than with Bozak over the past 4 seasons, so it makes for a difficult argument that Bozak is actually a better player than either of those guys or more deserving of #1 center role.

For Bozak, when he is not playing with Kessel (particularly the past couple seasons) he has generally been playing with 3rd line players like McClement, Kulemin, Raymond, Komarov, etc. in very defensive roles. This could have a significant negative impact on his without Kessel statistics. That said, over the past 2 seasons, Bozak’s CF% without Kessel is 27.5% and his GF% without Kessel is 37.5%. These are horrifically bad numbers and pretty difficult to justify, but could in part be due to Bozak being used to win defensive zone face offs when without Kessel. If he loses a defensive zone face off, he gets stuck on the ice for a bunch of shots against. If he wins the face off and Leafs clear the zone he heads to the bench getting no benefit of any subsequent offensive chances. This certainly would be a factor but I have serious doubts it is enough to justify a 27.5 Corsi percentage. Playing with Jay McClement a fair bit certainly doesn’t help, either, as McClement consistently put up poor possession statistics every year (that article is another example of how one can use WOWY’s in player evaluation).

I hope this provides a little more detail as to how one might conduct a WOWY analysis of a pair of players as a method of determining which players are more critical to the on-ice success of the team. In the example of Kessel and Bozak, there is little or no evidence that Bozak is integral to Kessel’s production where as there is a lot of evidence that Kessel is integral to Bozak’s production. As always, if you have any questions feel free to ask in the comments.

ICYMI: An Introduction to Advanced Statistics

To better understand this analysis, please see David Johnson’s post: A Guide to WOWYs

• MLHS_Luke

Wowy-we-woow!
Thanks David!

• MLHS_Luke

I personally find this stuff so hard to get a definitive answer from.  Like you infer, Bozak’s WOWY stats indicate he is riding on Kessel’s coattails.  However, you have to consider the linemates each player has when not playing with each other, the zone starts, the icetime (is pp time included in these stats?), the list goes on.

Interesting, nonetheless.

• http://www.thestar.com/ ManofMaple

Bozak played third line/penalty kill, I recall, under Wilson.
So much for the stats.

• BigTO

Thanks again David.
Lats season was Bozak’s best as a professional, but probably will be the best PPG he puts up in his career. I figure his prime production year was a little delayed by his path into pro hockey.  I’d love to be wrong.

• BigTO

I think why Bozak’s numbers are so horrifically bad without Kessel are
mostly explained by the two reasons you gave about dzone faceoffs and
linemates. That said, I  see the center as the biggest key to driving
possession and those numbers aren’t without a little concern for when Kessel and Bozak eventually play apart. MLHS_Luke

• vinoa

Another great article on MLHS. How does Bozak’s extremely low Corsi %age without Kessel compare to other players that play in similar roles (PK, defensive zone faceoffs etc.)? As much as I’d love to say that Bozak sucks, how valid are these numbers?

• BigTO

vinoa He doesn’t suck but he’s not a good driver of possession. He complements Phil pretty well. He kind of nips into the playe with a nice little touch here or there. He can finish and he reads the play well. He just can’t help the Leafs’ top line control possession against the best centers in the League.
I want to see a bigger sample of him away from Kessel before saying he couldn’t be a good 2 or 3c.

• vinoa

@BigTO The biggest knock on Bozie is that he’s been playing over his head. Only problem is that 2 head coaches at the NHL level have deemed him to be good enough to play on that 1st line. Are they seeing something that the stats aren’t showing? Or is Bozie proof that you really need to watch the game for the subtleties that numbers can mask? As you said, he does a lot of the little things well. This could be Dubas 1st challenge with real analytics.

• http://www.thestar.com/ ManofMaple

@BigTO vinoa
Most players get stronger physically every year.
I see Bozak gaining in breadth, solidity and strength over younger, taller centres and gaining on the veteran “big centres”.
Having said that, I thought he was excellent way back when he played third line, PK with Armstrong and … who was it.

• Burtonboy

Does replacing Bozak on the 1st line improve Kessel’s production enough to make up for the corresponding drop off in Bozak’s production if he’s moved off that line? From a team perspective we might be worse off in terms of overall production . I see no reason to move Bozak off that line just because his production is tied to playing with Kessel . Till we reach a point where we trade for a # 1 stud or someone like Kadri can make the case to be  # 1 I see no need to move him.

• Xxxxxnew

My eyeball observation last season was Kessel and JVR both seemed to fall off somewhat when Bozak was injured for a long stretch.

• Territory

Is there a point in replacing Bozak as the #1 centre if Kessel doesn’t even really improve with other guys? But Bozak gets worse, so it’s better for the team to have him on the top line. Until the Leafs get a centre that can make Kessel better, Bozak is the best choice.

The stuff about Bozak being used defensively, and for faceoffs, must be a big factor in his without him stats. Other then the season you mentioned, how much did Bozak really play without Kessel? He’s usually with him, so the sample sizes in those other seasons must be small too. Combined with the dzone faceoff and teamate problem, it could lead to his bad without him stats.

• BigTO

Xxxxxnew That’s where I disagree with the stats guys. Bozak was our best solution there last season, period, but we had a miserable center group. Kadri was in his first full season trying to adjust to playing 2nd line comp… there’s no way he could be expected to pop right in there and kill it without some patience. Bolland was hurt. McClement in above his head anywhere but at 4c.
Kessel and JvR played worse without Bozak because Bozak was the best solution there last season, period. But  no, he’s not the best solution long term.
#balance

• Habskilla

How many games has Bozak played without Kessel???

• peterbleafs

This article just proves Kessel plays well with any competent center.  The only thing it does not provide insight on is whether kessel does even better with a really elite centre.  So really, its a moot point anything discussed in here.

• Tim Horton

peterbleafs Kessel was amazing in the Olympics if that counts.

• Burtonboy

Territory Makes little sense to slightly improve or even maintain statue quo with Line number #1 and then make another line a lot worse by dropping Bozak back in the line up . It seems some people think its a crime that Bozak needs Kessel to produce . I say so what ,as long as he produces.

• Territory

Stats aside, Bozak is also an extremely versatille player that can play in any situation. PP, PK, 5on5, 4on4, etc. He can also play up and down the lineup if needed. That type of player is always valuable to have.

• Territory

Burtonboy Territory Agreed.

• Xxxxxnew

I also wonder how ‘chemistry’ fits into these numbers. Sometimes a couple of players just click together. Gretzky and Kurri were like two guys sharing the same brain on the ice. Brett Hull and Adam Oates were like a single unit. I’m sure their numbers were off the charts. But when they put Gretzky and Hull together in St. Louis they sucked.

• Jmessih

If Dubus is hired two years ago, is Bozak re-signed last summer? I’d say probably not, or at least if he is at a smaller dollar amount (Bozak’s contract is not an issue anyway).

• ShotgunCharlie

Territory And….he was free

• Alec Brownscombe

Territory Yep, I agree. Just isn’t anything close to a 1C stud, which for 4.2 million, he isn’t paid to be.
It’s mgmt’s job to fill that need for a 1C. We’re waiting and waiting. Hopefully Nylander is it.

• http://mapleleafshotstove.com/ Ian from Etobicoke

Territory Just not as the most important skater on the team.

• Xxxxxnew

He and Savard looked good together in Boston as well.

• Mcost61

• Xxxxxnew

1C has certainly become the hardest spot to upgrade across the league, let alone the Leafs. For the type of guy we’d like, anyway.

• Walter_White

Alec Brownscombe I’d like to see the coaching staff experiment with Lupul – Kadri – Kessel, and JVR – Bozak – Clarkson. I know Kessel and JVR have chemistry, but I think the top line would still produce and perhaps new line mates could help Clarkson reinvent himself in TO.

• Xxxxxnew

Couldn’t have done that without a backup plan,tho.

• BPsotka

I’d like it if the introduction to analytics article was linked to the bottom. Thought it was really useful and would be good to reference while reading this (and I’m sure more statistical analytic articles to come).

• Bobsyouruncle

Territory
He CAN play on the PP but what’s the point? He had 8 fucking PP points last year.

• Bobsyouruncle

Habskilla
Who friggin knows?
Apparently he “can play up and down the lineup” lol, even though we’ve never seen him do anything but be with Kessel.
For this to work maybe Kessel will have to play “up and down the lineup ” with him.  : )

• Xxxxxnew

Toughest spot to fill in the cap era I’m thinking. For the kind of C we want.

• Bobsyouruncle

Territory
Your talking shit. How about we see another centre get a chance with Kessel.

• NiagaraFallsThunder

Alec Brownscombe Territory All things considered, who are some other centres around the 4.2 range and how does he compare to them in terms of production?

• Mcost61

Xxxxxnew  Savard was a true playmaker, we need one of those

• Greg Fenton

vinoa The two aren’t related.

Two coaches deeming him good enough to play on the Leafs #1 line just means that the Leafs don’t have a better option.

• Walter_White

Leaf fans are the best. Regardless of what we think of Bozak, our top line was one of the best in the league. But we get all bent out of shape because it could/should be better. Meanwhile our bottom 6 was beyond brutal, and our D was pretty much an embarrassment night in and night out. Yet we continue to gripe about Bozak. There are so many places on the roster that stress me out more than JVR-Bozak-Kessel. (Note: this was not a shot at the author or the article, which was great. Just a general observation.)

• hockeyanalysis

Burtonboy Bozak’s away from Kessel numbers are terrible though zone starts and other situational factors are at play there. There is no evidence he makes those 3rd liners produce any better or perform any better defensively though.

Until this past season all evidence pointed to him having a negative impact on Kessel’s offensive production. One year doesn’t reverse that trend but we’ll see if he can repeat. The challenge is, we haven’t really seen Bozak in a secondary offensive role. Can he put up good numbers on a second line without Kessel and JVR/Lupul? I don’t know. Maybe, he just hasn’t been given that opportunity. I am not sure he is suited for a defensive role either. There is little evidence of that.

I personally think the team would be best off with Kadri in #1C role and then let Bozak fight it out with the other centers for 2nd or 3rd line roles. Is he better than Holland? Maybe. Does Holland have more potential upside? Quite possibly. I am not a big Bozak fan but I’ll give him the benefit of doubt after a pretty decent season last year.

• Greg Fenton

Walter_White It was one of the best in the league……at times. At other times it wasn’t very good and/or productive, and because of those stretches they missed the playoffs. Why shouldn’t people be bent out of shape about that?

• Walter_White

Greg Fenton We missed the playoffs because no other line could pick up the slack when our top line didn’t produce (which is to be expected over an 82 game season).

• hockeyanalysis

BPsotka It’s linked at the top of the article if that helps.

• Greg Fenton

Walter_White Greg Fenton Its both.

No other line could score as much as the Leafs top line, but is it realistic to expect that? I don’t anyone they added this year can score like that. But why couldn’t the Leafs top line score consistently?

• hockeyanalysis

@ManofMaple Yes, though I think more to win a key face off than for his defensive ability. Often left the ice after team gained control.

• Mcost61

Greg Fenton Walter_White  Scoring was not our problem. Letting other people score is Our PK and GAA were horrendous, middle of pack in scoring

• Burtonboy

hockeyanalysis Burtonboy The concern I have is will we create another line that would be far worse production then it presently might be by moving Bozak down to say 2nd or 3rd line . Would Kessel playing with Kadri seen a spike up to compensate for that overall loss in production? I’m game to try Kadri as #1 C just unsure of the results at this point.

• Greg Fenton

Mcost61 Greg Fenton Walter_White At times it was.

• Walter_White

Greg Fenton I don’t think anyone would expect another line to produce as much as them, but our secondary scoring was so bad last season, particularly from the bottom 6. We can’t expect the top line to carry us for 82 games. They carried our offense all season and then sputtered at the end and nobody could pick up the slack. Good teams don’t have that problem.

• Mcost61

Greg Fenton Mcost61 Walter_White  Having the puck more will do great things

• Greg Fenton

Walter_White Greg Fenton It was, I’m not denying the bottom 6 needs to produce more. But its silly to pretend that the top line didn’t suck for periods of time and play a big role in the team’s two big losing streaks. And we SHOULD be bent out of shape about that.