Wouldn't +/- be much better if

patnyrnyg

Registered User
Sep 16, 2004
10,848
873
The idea of giving a + to a guy who drew the penalty and a goal was scored on the ensuing PP? I would say only if that player was on for the PPG being scored. If a 4th liner draws 2 PP's in a game, but the PP units can't generate anything on those 2 PP's it doesn't take away from the 4th liner drawing the PP. Yet another player on the team could draw a questionable penalty at best, opposing goalie gives up an awful goal and the player drawing that penalty gets a +? Just doesn't seem right.

As others have said, +/- is pretty much a useless stat. Only time I think it can be helpful is one of the following scenarios:

1) Player is a - on a really good team.
2) Player is a + on a really bad team.
3) Player is a -, yet a pretty high scorer.

1 and 3 are red flags to me, but in all 3 scenarios I think further investigation is warranted to explain/figure out why the player is in the scenario.
 

The Panther

Registered User
Mar 25, 2014
19,184
15,740
Tokyo, Japan
Here's a starting point for something along the lines of "Individual Value":

First, as I said before, I don't know that this will work well at all for players that derive the vast majority of their value from ES defense (shutdown d-men and checking forwards).
Second, while I think something like this could work well for comparing at least certain types of players within a single season, there would need to be further adjustments to compare players from different seasons. For one, ES/PP/SH scoring levels vary from season to season, which allows more value to be apparently created in some seasons compared to others, so one would have to adjust for scoring levels. Also, parity varies from season to season, which should affect replacement level (since I'm basing it here on the worst team in the league in that particular category). A solution might be to use an average or median for a multi-year period, to smooth out variations due to randomness and/or differing environments (e.g., expansion or otherwise unusually bad teams). Finally, another issue may be scale, such that comparing skaters to goalies (using goals saved vs. league avg. or replacement level) may not be possible, since the scale of the metrics for each may be different.

Panther used '94 Gretzky as an example, so I'm comparing '94 Gretzky to '94 Fedorov.

Even Strength Value

One starting point would be Adjusted Plus-Minus: Adjusted Even-Strength Plus-minus 1960-2017 | HFBoards - NHL Message Board and Forum for National Hockey League (mandatory.com)

Basically, we calculate ESGF & ESGA from TGF, PGF, TGA & PGA.
ESGF = TGF - (PGF + SGF) ... SGF is estimated from team SGF and the individual's ratio of PGA (individual PGA/team PGA). One difference is that if individual's SHP (SHG + SHA) were more than the estimate, I used SHP instead of the estimate (since it had to be at least that much).
ESGA = TGA - (PGA + SGA) ... SGA is estimated from team SGA and the individual's ratio of PGF (individual PGF/team PGF).

Once we have individual ESGF & ESGA, "OFF" (team's ESGF & ESGA) is easily derived from (Team - Individual) for each of ESGF & ESGA.

Overpass, the author of that study, regressed the expected plus-minus (using OFF) to average (1.0), but I am not bothering with that here (although I'm not necessarily against) for the sake of simplicity.
The regression he does favors players on above average ES teams and penalizes players on below average ES teams (again, I'm not saying that's necessarily unjustified).

Without regressing to average, the adjusted plus-minuses are: Gretzky -12.8 & Fedorov +35.4
The raw (ESGF - ESGA) are: Gretzky -25.2 & Fedorov +45.4 ... Overpass' adjusted plus-minus would be between the two numbers (i.e. Gretzky -12.8 to 25.2, Fedorov +35.4 to 45.4), so in this case not regressing to the average yields a smaller gap between the two players.

I also calculated ESV another way. I gave the player credit for ESGF based on his ES points (ESG + ESA), but penalized him for ESGA based on him being one of five skaters on the ice. Before I go through the details of the calculation, I should say that I think it would be fairest to first adjust ESGA for team SV% vs. league average, but I didn't do that here (this again favored Gretzky, since Kings were around league avg., while Wings were worse).

Gretzky had 20 ESG & 42 ESA, while he was on ice for an estimated 77.0 ESGF. So he had points on 62/77 ESGF or 80.5%. His team had 479 ESP on 183 ESGF or 2.62 points awarded per ESGF.
Dividing 80.5% by 2.62, we get 30.8% and will call this his ESGF Responsibility %. We divide Responsibility for ESGA equally among each of the five skaters (this is an assumption for simplicty, the actual number would be slightly lower), so 20% each. We do the same for Fedorov, who had points on 75.0% of ESGF.

This yields these numbers:
Gretzky: ESGF = 77.0 * .308 = 23.7 ; ESGA = 102.2 * .20 = 20.4... so +3.3
Fedorov
: ESGF = 108.0 * .287 = 31.0; ESGA = 62.6* .20 = 12.5... so +18.5

Power Play Value


We're using the worst team in the league in that category as "Replacement Level." So the Kings converted 20.7% of their PPs, while the Ducks only converted 14.4% of their PPs. We multiply the difference by the Kings' PP opportunites to yield: 444 PPO * (.207 - .144) = 28.2 Goals Above Replacement Level. So how do we distribute part of those 28.2 GARL to Gretzky? He had 14 PPG & 47 PPA for 61 PP points on 78 PGF, so 61/78 = 78.2%. Dividing 78.2% by 2.89 points awarded per Kings PP goal, we get 27.0% for his PGF Responsiblity %. We multiply that by the 28.2 GARL for his team to get 18.7 GARL for PGF. We do the same for Fedorov to get 9.5 GARL for PGF.

We calculate how many SGA were saved by using the same methodology for SH goals given up (but equally divided among five or 20% each), which yields Gretkzy 2.5 & Fedorov 0.9

PPV Totals: Gretzky = 18.7 +2.5 = 21.2; Fedorov = 9.5 + 0.9 = 10.4

Short Handed Value

Using the same methodology for SGF as for PGF, we get: Gretzky 3.0 & Fedorov 4.9 for GARL while SH.

We calculate how many PGA were saved by using the same methodology as For SGA (excep tequally divided among four for 25% each) which yields: Gretzky 8.3 & Fedorov 8.8

SHV Totals: Gretzky = 3.0 + 8.3 = 11.3; Fedorov = 4.9 + 8.8 = 13.8

Summary


ESV
---Simple (ESGF - ESGA): Gretzky -25.2, Fedorov +45.4
---"Raw" Adjusted Plus-Minus: Gretzky -12.8, Fedorov +35.4
---Responsibility %: Gretzky +3.3, Fedorov +18.5

PPV: Gretzky 21.2, Fedorov 10.4

SHV: Gretzky 11.3, Fedorov 13.8

TOTALS, Using
---Simple (ESGF - ESGA): Gretzky +7.4, Fedorov +69.5
---"Raw" Adjusted Plus-Minus: Gretzky +19.8, Fedorov +59.6
---Responsibility %: Gretzky +35.8, Fedorov 42.6

The first two are rather large gaps. Another thought is that perhaps, assuming the line of three forwards is driving ES advantage/disadvantage, is to divide those numbers (Simple ESGF-ESGA & Raw Adj. PM, since Resp.% already distributes the advantage/disadvantage) by three. If we did this and made the adjustment for SV% vs. league avg., the gaps between Gretzky & Fedorov would be about 17, 10 & 8 goals, respectively. That range seems reasonable to me, but I welcome any comments or suggestions.
I can't really understand this, but it seems rather amazing.
 

Czech Your Math

I am lizard king
Jan 25, 2006
5,169
303
bohemia
I can't really understand this, but it seems rather amazing.

I think it has potential to be somewhat amazing (more like a good ballpark estimate for player value for more scoring-oriented skaters, particularly forwards).

The toughest part is integrating ES value with the other components. One problem is that in the version which I posted, ES value is based on vs. average and is zero sum, while the components are based on vs. replacement level and have a positive sum. This isn't so much a problem within a single season, but is when comparing across seasons. Another problem is that for the best players, the credit which they receive (responsibility %) for ESGF (and possibly other GF) may be less than their actual impact. If there were 2.7 points awarded on average for every ESGF, then even if a player had points on 100% of his ESGF, the most credit he would receive is 1/2.7 = 37% for each ESGF. However, when we're dealing with the best player on each line/unit, and particularly with some of the very best players ever, it seems likely that they drove scoring to a higher degree than 37% (and no player is going to have 100% ESP/ESGF ratio, so it's going to be capped at something more like 32%). It also assumes players share ESGA equally, which on one hand doesn't penalize poorer defensive players, and OTOH gives forwards as much defensive responsibility as d-men and doesn't account for great possession players' possession as a form of defense (preventing goals by possessing puck).

The special teams components are a lot easier to explain. Value is created by the team on special teams by being better than replacement level (league worst team in each category). Player value is created by being responsible for a portion of team value, which is calculated either from % of teams' points scored in that special teams category or estimated time played no that special team (from GF & GA data). If one used league average as the baseline, then it would be zero sum, but it would also give many players negative special teams value. This doesn't seem ideal, since it would then be more beneficial to the player to not play on special teams at all (yet their team found it to be valuable to have them play on special teams). The solution I chose was to use the worst team in each category as a "Replacement Level." That means no team will have negative value on each category of special teams.

I have changed the methodology a little bit already and also found a formula error. This is the general concept I have for special teams:

Team's Special Teams % (PP%, PK%, SHGF%, SHGA%) = ST%

League's Worst Team in that Category = RL%

Absolute value of (ST% - RL%) = % Difference

Team's Opportunities in that Category (e.g., PPO) * % Difference = Goals Above Replacement Value (GARV) for that Category

Apportionment of Team's GCV for that Category Among Individuals = GARV * (Player's Total Points in that Category)/(Team's Total Points in that Category)

------

So for Gretzky's/Kings' PP:

LAK PP% = .2072 (20.72%)

ANA (league worst) PP% = .1436 (14.36%) = Replacement Level [Note: We want league worst %, not raw number of GF or GA]

Difference = (.2072 - .1436) = .0636

LAK PPGF GARV = .0636 * 444 PP Opportunities = 28.2 GARV

So the difference betweent the Kings' and the league-worst (ANA) power play, given the Kings' 444 PP opportunities, was 28.2 goals.

Gretzky had 14 PPG & 47 PPA for 61 PP points. Kings had 92 PPG & 174 PPA for 266 points awarded on PP. So Gretzky's given credit for 61/266 = 22.9% of their power play goals above replacement level (PP GARV).

So we multiply Kings' PP 28.2 GARV by Gretzky's 22.9% (PPGF Responsibility %) and get 6.5 goals, so the PGF component of Gretzky's power play value (PPV) is +6.5 goals.

-------

The other component of PPV is SGA (shorthanded GA).

LAK gave up 8 SGA on 444 PPO or .0173 (1.73%)

TB (league worst) gave up 20 SGA on 335 PPOA or .0515 (5.15%)

Difference = (.0515 - .0173) = .0342

LAK SGA GARV = .0342 * 444 PPOA = 14.9 GARV

Gretzky was on ice for 78 of the Kings' 92 PGF, so his PP ice time is estimated as 78/92 or 84.8%

We assume 5 players on ice fore each PP (actual number slightly lower), so Gretzyk's given credit for 27.6 GARV * .848/5 = 2.5

So his PPV = 6.5 + 2.5 = 9.0 GARV

You use the same processes for SHV (SHP for SGF, PGA to estimate % on PK).

The real work to be done is to find a fair and accurate value for ES value that also scales properly to integrate it with the special teams components and allows for fair cross-season comparisons.
 
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Hockey Outsider

Registered User
Jan 16, 2005
9,115
14,281
I think it has potential to be somewhat amazing (more like a good ballpark estimate for player value for more scoring-oriented skaters, particularly forwards).

The toughest part is integrating ES value with the other components. One problem is that in the version which I posted, ES value is based on vs. average and is zero sum, while the components are based on vs. replacement level and have a positive sum. This isn't so much a problem within a single season, but is when comparing across seasons. Another problem is that for the best players, the credit which they receive (responsibility %) for ESGF (and possibly other GF) may be less than their actual impact. If there were 2.7 points awarded on average for every ESGF, then even if a player had points on 100% of his ESGF, the most credit he would receive is 1/2.7 = 37% for each ESGF. However, when we're dealing with the best player on each line/unit, and particularly with some of the very best players ever, it seems likely that they drove scoring to a higher degree than 37% (and no player is going to have 100% ESP/ESGF ratio, so it's going to be capped at something more like 32%). It also assumes players share ESGA equally, which on one hand doesn't penalize poorer defensive players, and OTOH gives forwards as much defensive responsibility as d-men and doesn't account for great possession players' possession as a form of defense (preventing goals by possessing puck).

The special teams components are a lot easier to explain. Value is created by the team on special teams by being better than replacement level (league worst team in each category). Player value is created by being responsible for a portion of team value, which is calculated either from % of teams' points scored in that special teams category or estimated time played no that special team (from GF & GA data). If one used league average as the baseline, then it would be zero sum, but it would also give many players negative special teams value. This doesn't seem ideal, since it would then be more beneficial to the player to not play on special teams at all (yet their team found it to be valuable to have them play on special teams). The solution I chose was to use the worst team in each category as a "Replacement Level." That means no team will have negative value on each category of special teams.

I have changed the methodology a little bit already and also found a formula error. This is the general concept I have for special teams:

Team's Special Teams % (PP%, PK%, SHGF%, SHGA%) = ST%

League's Worst Team in that Category = RL%

Absolute value of (ST% - RL%) = % Difference

Team's Opportunities in that Category (e.g., PPO) * % Difference = Goals Above Replacement Value (GARV) for that Category

Apportionment of Team's GCV for that Category Among Individuals = GARV * (Player's Total Points in that Category)/(Team's Total Points in that Category)

------

So for Gretzky's/Kings' PP:

LAK PP% = .2072 (20.72%)

ANA (league worst) PP% = .1436 (14.36%) = Replacement Level [Note: We want league worst %, not raw number of GF or GA]

Difference = (.2072 - .1436) = .0636

LAK PPGF GARV = .0636 * 444 PP Opportunities = 28.2 GARV

So the difference betweent the Kings' and the league-worst (ANA) power play, given the Kings' 444 PP opportunities, was 28.2 goals.

Gretzky had 14 PPG & 47 PPA for 61 PP points. Kings had 92 PPG & 174 PPA for 266 points awarded on PP. So Gretzky's given credit for 61/266 = 22.9% of their power play goals above replacement level (PP GARV).

So we multiply Kings' PP 28.2 GARV by Gretzky's 22.9% (PPGF Responsibility %) and get 6.5 goals, so the PGF component of Gretzky's power play value (PPV) is +6.5 goals.

-------

The other component of PPV is SGA (shorthanded GA).

LAK gave up 8 SGA on 444 PPO or .0173 (1.73%)

TB (league worst) gave up 20 SGA on 335 PPOA or .0515 (5.15%)

Difference = (.0515 - .0173) = .0342

LAK SGA GARV = .0342 * 444 PPOA = 14.9 GARV

Gretzky was on ice for 78 of the Kings' 92 PGF, so his PP ice time is estimated as 78/92 or 84.8%

We assume 5 players on ice fore each PP (actual number slightly lower), so Gretzyk's given credit for 27.6 GARV * .848/5 = 2.5

So his PPV = 6.5 + 2.5 = 9.0 GARV

You use the same processes for SHV (SHP for SGF, PGA to estimate % on PK).

The real work to be done is to find a fair and accurate value for ES value that also scales properly to integrate it with the special teams components and allows for fair cross-season comparisons.

CYM, are you familiar with Alan Ryder's Player Contribution? Link - Player Contribution

This is, as far as I'm concerned, the gold standard for performance measure for an individual player. The most obvious downside is it's incredibly convoluted and the results are only available between 2004 and 2011.

It sounds like your approach is similar in many ways (the biggest divergence being ES - he's looking at offense and defense separately, and you're combining them).
 

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