Can forwards affect SV%

[BarryBSB]

First post here btw so hello to all of you.

Over at a Rangers fan blog an article was posted discussing the fact that over the last 4 seasons, when Derek Stepan is on the ice (1,872 5v5 shots against), Ranger goalies have a 94.71 save percentage. When he is off the ice (4,805 5v5 shots against) Ranger goalies have a 92.40 save percentage. We (I'm a regular commenter there and am participating in the discussion) are not sure what this means and how it could even be possible. I'd love to get some outside eyes and was hoping you guys would be interested.

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[Caeldan]

As a center if he's defensively responsible I can see that being plausible.

After all, his job is to cover the dangerous area of the ice on defense. So if he's preventing those high % shots, or turning them into less dangerous ones it'll be reflected in the goalie's sv%

Whether there's enough events over the course of a season to make it something statistically significant I'll leave to someone who's better at numbers than me.

 

[Michael Farkas]

Absolutely. For the reasons mentioned above, particularly. Most centers are relied upon heavily in typical in-zone coverage schemes. They come lower than the wingers who will normally stay out at the points (of course, alterations can be made to adjust for circumstance - Kurri taking on the center's defensive responsibilities for Gretzky, for instance). Conscious defensive centers can limit the quality of chances against certainly.

 

[BarryBSB]

The weird thing is that if on-ice Sv% is something Stepan can control, he's a lot better at it than the rest of the leagues premier 2-way centers, guys like Bergeron, Kopitar, and Teows.

 

[Tavares2TheRescue]

Short answer: no.

Long answer:

If we can learn something from a player’s on-ice shooting percentage, you might be wondering whether the equivalent stat exists for another commonly cited percentage: save percentage. And it does, which is lucky for us since otherwise this whole section would be pretty dull.

On-ice save percentage is basically what the name implies: the percentage of shots directed at his team’s net that are saved when a particular player is on the ice. It should probably go without saying that a player’s on-ice save percentage is heavily influenced by his team’s goaltending, which is why leaguewide comparisons are less useful here. But we’ll often see pretty wide gaps even among players on the same team, especially over small samples. So let’s go back to that key question: Are we seeing the result of luck or skill?

Again, the common-sense approach might assume there has to be a large skill component involved. A bad defensive player gives up breakaways and odd-man rushes and leaves men open in the defensive zone. Meanwhile, the Zdeno Charas of the world force everything to the outside and make opponents settle for low-percentage chances.

But unlike on-ice shooting, there doesn’t seem to be much consistency across players when we look at on-ice save percentage. While the on-ice shooting leaderboard features plenty of offensive stars, the top players in on-ice save percentage are a mishmash of grinders, first-liners, two-way guys, and enforcers. When Teemu Selanne is close to Brian McGrattan, something weird is going on.

In fact, when you stretch the view out over several years, it starts to look almost random, especially among forwards. (Defensemen are a little more predictable, but not by much.) There seems to be an awful lot of luck involved here.

And that’s a pretty important piece of information to know, because though on-ice save percentage doesn’t directly affect a player’s goals and assists, it can certainly affect his plus/minus. (I’ll pause here to remind you that plus/minus is an awful stat that should almost always be avoided entirely, partly for this exact reason.)

And perhaps more importantly, it can affect how the player is perceived by the “just watch the games†crowd. A player who benefits from a great on-ice save percentage never seems to get scored on, while a player with a low percentage always seems to be skating to the bench with his head down while a goal horn blasts.

For a stat that players don’t seem to have all that much control over, on-ice save percentage sure can drive a narrative (as demonstrated brilliantly here). But most of that ends up being unfair.

http://grantland.com/the-triangle/your-guide-to-nhl-on-ice-percentages/

 

[Michael Farkas]

So, for this particular stat "they" - whoever that may be - don't like the results and discard it...yet when a complete loser like Tyler Kennedy is a bad-shot generating machine, he's a "great possession player"...and a terrific defensive player like Brandon Sutter has low shot attempts, he's a "blackhole"...that seems odd to me...

I took a peek at the top-30 centers (min. 50 games played) in on-ice save pct. and it is a lot of players known for their two-way or defensive ability...then also players like Olli Jokinen and Zach Sill too...but that could be adjusted for their matchups or whatever...

Just like the usat top scores contain guys like Trevor Lewis, Patrik Berglund, Darren Helm and Colton Sceviour...what's the difference...? None of them are exactly whiz kids with the puck...

It seems like all of these stats and any other stat really...it can suggest some things, but doesn't give the whole story and is ripe with exceptions...what's the big deal about this one not being "counted", so to speak...?

 

[BraveCanadian]

So, for this particular stat "they" - whoever that may be - don't like the results and discard it...yet when a complete loser like Tyler Kennedy is a bad-shot generating machine, he's a "great possession player"...and a terrific defensive player like Brandon Sutter has low shot attempts, he's a "blackhole"...that seems odd to me...

I took a peek at the top-30 centers (min. 50 games played) in on-ice save pct. and it is a lot of players known for their two-way or defensive ability...then also players like Olli Jokinen and Zach Sill too...but that could be adjusted for their matchups or whatever...

Just like the usat top scores contain guys like Trevor Lewis, Patrik Berglund, Darren Helm and Colton Sceviour...what's the difference...? None of them are exactly whiz kids with the puck...

It seems like all of these stats and any other stat really...it can suggest some things, but doesn't give the whole story and is ripe with exceptions...what's the big deal about this one not being "counted", so to speak...?

Well one reason would be that if they have to admit that players can affect save percentage through their defensive play, then they also have to admit that the quality of scoring chances does matter and the "luck" involved in that variation does not necessarily equal out over time. Same with shooting percentage. I swear that some players are better shooters than others.. maybe it is just me.

Stuff like this throws a wrench in a lot of the things people have been spouting off about for a while. So many variables..

 

[BarryBSB]

As far as I know, conventional #fancystats wisdom agrees that certain players can maintain higher shooting percentages over time, and there are players who have above average shooting percentages their whole career. The same community doesn't believe skaters can really affect save percentage because they've seen no proof of players being able to maintain it year after year, implying that it's just luck.

I brought up the Derek Stepan example as seemingly an exception to the rule, because his on-ice save percentage has been better than the team's for 4 straight years. It is possible he got lucky four years in a row, seems unlikely though.

 

[Doctor No]

I brought up the Derek Stepan example as seemingly an exception to the rule, because his on-ice save percentage has been better than the team's for 4 straight years. It is possible he got lucky four years in a row, seems unlikely though.

Wouldn't you expect 1 out of 16 players to have on-ice save percentages better than their team's for four straight years, even if it were completely random?

 

[charlie1]

First post here btw so hello to all of you.

Over at a Rangers fan blog an article was posted discussing the fact that over the last 4 seasons, when Derek Stepan is on the ice (1,872 5v5 shots against), Ranger goalies have a 94.71 save percentage. When he is off the ice (4,805 5v5 shots against) Ranger goalies have a 92.40 save percentage. We (I'm a regular commenter there and am participating in the discussion) are not sure what this means and how it could even be possible. I'd love to get some outside eyes and was hoping you guys would be interested.

Sounds like a multiple comparisons problem to me. See Doc's post above.

That said, within-season forward Sv% is SLIGHTLY predictable (i.e., not completely random).

See emmanuel perry's work:

https://public.tableau.com/profile/emmanuelperry#!/vizhome/SampleSizeAnalysis/Dashboard1

 

[eklunds source]

As far as I know, conventional #fancystats wisdom agrees that certain players can maintain higher shooting percentages over time, and there are players who have above average shooting percentages their whole career.

Shooting percentages are largely driven by shot location and not "shooting talent" -- the closer you are to the net, the more likely your shot will go in. Players who maintain higher shooting percentages typically do so by taking (or setting up) a higher percentage of their shots from closer in.

A tale of two talents

I looked at whether some players exhibited an ability to score more often from a given spot on the ice than other players. This "talent" regressed 75% to the mean, and a high level of skill was really only identifiable in Ilya Kovalchuk and Alex Tanguay:

Compare that to a "legitimate" talent - getting to a good spot on the ice and taking a shot from there. A player's ability to get to his shooting locations regresses just 11% to the mean - in other words, a player controls where he gets opportunities from, and it is an inherent part of his play, unchanged from game-to-game:

Where players spend their time in the offensive zone

So if we look at even-strength shots taken by Andrew Brunette over the last five seasons, we see a player who spends his time very close to the goal (0,0) - it's no surprise that he led the league in shooting percentage last season.

The same community doesn't believe skaters can really affect save percentage because they've seen no proof of players being able to maintain it year after year, implying that it's just luck.

Your assessment (on-ice save percentage is essentially luck) is correct; your reasoning is not. It has nothing to do with "no proof"; it is because if you test the group as a whole, you will find that there is very little reliability in year-to-year on-ice save percentage.

Save percentage variability regression

There were 127 forwards who were on the ice for 1000 5-on-5 shots in both the three-year period from '07-10 and the three-year period from '10-13. Their on-ice save percentage over the first three years was essentially useless as a predictor of how they'd do in the next three years:

Over a three-year span, it doesn't matter whether a forward sees his team stop 94% or 90% of the shots with him on the ice at 5-on-5; either way, the best guess for how he'll do in the next three years is league average. If there are differences between players in their ability to influence the opponents' shooting percentage, those differences are much less than whatever other random factors come into play.

 

[tfong]

I definitely am of the opinion that forward defensive skill affects QoS.

 

[eklunds source]

So, for this particular stat "they" - whoever that may be - don't like the results and discard it...yet when a complete loser like Tyler Kennedy is a bad-shot generating machine, he's a "great possession player"...and a terrific defensive player like Brandon Sutter has low shot attempts, he's a "blackhole"...that seems odd to me...

Even when your team is taking "bad" shots, you still have to have control of the puck, in or near the offensive zone. If you have possession of the puck, the other team doesn't, and if the other team doesn't have possession, they can't score.

I took a peek at the top-30 centers (min. 50 games played) in on-ice save pct. and it is a lot of players known for their two-way or defensive ability...then also players like Olli Jokinen and Zach Sill too...but that could be adjusted for their matchups or whatever...

The problem is that 50 games means absolutely nothing. This year, the worst Boston Bruin forward in on-ice sv% was Patrice Bergeron -- at 0.901 through 81 games. Gregory Campbell played in 70 games and his on-ice sv% was 0.950.

For Bergeron, 1 out of every 10 shots against went in the net.
For Campbell, 1 out of every 20 shots against went in the net.

...and that's over a full season -- Campbell played 718 minutes, Bergeron played 1048.

It seems like all of these stats and any other stat really...it can suggest some things, but doesn't give the whole story and is ripe with exceptions...what's the big deal about this one not being "counted", so to speak...?

The problem isn't the statistic -- the problem is that people attribute meaning to it. Humans are very poorly equipped to deal with large data sets.

 

[eklunds source]

I definitely am of the opinion that forward defensive skill affects QoS.

...and yet we have almost a full decade of data that completely contradicts that. Perhaps you could explain how Boston goalies posted a 0.901sv% behind Patrice Bergeron this year (after 4+ years of a 0.930+ sv%) -- did the best defensive forward in the league suddenly and completely forget how to play defense?

 

[BarryBSB]

Interesting stuff guys. Thanks for chiming in

 

[tfong]

...and yet we have almost a full decade of data that completely contradicts that. Perhaps you could explain how Boston goalies posted a 0.901sv% behind Patrice Bergeron this year (after 4+ years of a 0.930+ sv%) -- did the best defensive forward in the league suddenly and completely forget how to play defense?

Off the top of my mind there are several scenarios at play here.

1) Bergeron had a bad year in defensive coverage comparatively to his other years.

2) Bergeron had a great year defensively but due his ability to interrupt dangerous plays and shots, the volume of shots going against Boston goalies was lower, so each goal scored now becomes a larger percentage.

3) Rask had a down year, as exhibited by his 0.922 vs prior 0.930, 0.929, 0.929. Despite Bergeron playing well defensively, Rask just wasn't as good this year

The problem with on ice sav as used in this thread is that it does not take into account mitigation of shot attempts . If Bergeron allows the opposition to take only 5 shots on net when he is on the ice and the shooter scores once, it is 1/5.

If a defensively poor center allows 20 shots on net while on ice, the goalie has to let in 4 goals in order for the number to match up to Bergeron's number.

Or a containment center who plays positionally well but allows shots from the outside would have a way higher sav% versus a pursuit defensive center that takes away shooting opportunities because shot volume goes down. This could be a direct scenario as well if Bergeron was concentrating on takeaways this year versus prior years he was looking to just box out opponents.

 

[BraveCanadian]

...and yet we have almost a full decade of data that completely contradicts that. Perhaps you could explain how Boston goalies posted a 0.901sv% behind Patrice Bergeron this year (after 4+ years of a 0.930+ sv%) -- did the best defensive forward in the league suddenly and completely forget how to play defense?

The team regressed around him?

He takes the tough matchups that a prime and/or healthy Chara would also be on the ice for... just as one example

 

[eklunds source]

The team regressed around him?

He takes the tough matchups that a prime and/or healthy Chara would also be on the ice for... just as one example

Off the top of my mind there are several scenarios at play here.

1) Bergeron had a bad year in defensive coverage comparatively to his other years.

2) Bergeron had a great year defensively but due his ability to interrupt dangerous plays and shots, the volume of shots going against Boston goalies was lower, so each goal scored now becomes a larger percentage.

3) Rask had a down year, as exhibited by his 0.922 vs prior 0.930, 0.929, 0.929. Despite Bergeron playing well defensively, Rask just wasn't as good this year

My question was rhetorical -- there could very well be a logical reason, but my point is that there doesn't have to be, and it's extremely unlikely that there actually is a reason.

Every forward who sees regular NHL minutes has a similar graph - lots of inexplicable peaks and valleys. It's the nature of the measurement, not something that requires logic.

 

[tfong]

Sorry so just to clarify since you were using a rhetorical question.

You believe there is a relation between on ice sav% and whether the forward is good defensively? Or that you believe there is an insignificant correlation?

 

[Tavares2TheRescue]

Well one reason would be that if they have to admit that players can affect save percentage through their defensive play, then they also have to admit that the quality of scoring chances does matter and the "luck" involved in that variation does not necessarily equal out over time. Same with shooting percentage. I swear that some players are better shooters than others.. maybe it is just me.
Stuff like this throws a wrench in a lot of the things people have been spouting off about for a while. So many variables..

No one has ever said that players can't sustain high shooting percentages. No one is going to say Stamkos can't sustain his 17%, because he's shown that he can. However, players can not be expected sustain shooting percentages greatly above their own career averages, because they've never shown to be that good of a shooter in the past. What you might be getting confused by is players' on-ice shooting percentages, meaning the combined shooting percentage of their entire team when that player is on the ice. That is not particularly sustainable for most forwards, but a few highly talented players can sustain percentages above the mean and a few awful players can be significantly below.

 

[eklunds source]

Sorry so just to clarify since you were using a rhetorical question.

You believe there is a relation between on ice sav% and whether the forward is good defensively? Or that you believe there is an insignificant correlation?

It's not what I believe, it's what is true Whatever ability a forward has to affect his goaltenders' save percentage is so tiny that it's buried by randomness. You're always going to find outliers -- players who seem to have an abnormally high or low on-ice sv% -- that doesn't mean those players are causing it.

 

[BarryBSB]

You're always going to find outliers -- players who seem to have an abnormally high or low on-ice sv% -- that doesn't mean those players are causing it.

What size sample would it take to make you reconsider that position? Because Stepan has done this for 4 straight seasons.

 

[Doctor No]

What size sample would it take to make you reconsider that position? Because Stepan has done this for 4 straight seasons.

I mentioned above that given a sample of 16 players, you would expect one to outperform the team average in four straight seasons solely due to random chance.

That person might be Stepan.

 

[BarryBSB]

I mentioned above that given a sample of 16 players, you would expect one to outperform the team average in four straight seasons solely due to random chance

Hypothetically, what if he were to do this for 10 straight seasons?

 

[Doctor No]

Hypothetically, what if he were to do this for 10 straight seasons?

There'd be a 1 in 1024 chance of this happening randomly.

Although there aren't 1000 players with that longevity in the league at any one time (note that a player who had this happen randomly might get more opportunities due to perceived ability differential), I would expect about one player in the league to have this happen.