Apology Required?

The General Idea

The Y-axis is Corsi differential (shots directed at net) at 5V5 for 2008/2009.

The X-axis is Shifts Ending with Faceoffs by Zone (Offensive - Defensive) at 5V5 for 2008/2009.

The blue dots are the Oilers skaters.

The red dots are the Flames skaters.

I think we can see the problem here.

Keeping Your Powder Dry

There are basically two ways to build a Stanley Cup contender and it doesn't seem that the Oilers have been following either approach:

1) Suck for a pretty long time. Three years is a good start, but you might need an extra year or two depending on your drafting record.

Or...

2) Build a reasonably cheap team and collect some prospects and picks in the event that an elite player in his prime hits the market. Joe Thornton and Chris Pronger come to mind as examples and there have certainly been others.

I recall Tyler Dellow used the title phrase to describe this latter strategy back when the Oilogosphere was mostly on the messageboards and I think it's a good way to think about it. Plus with Pat Quinn as the new head coach old-timey phrases are de rigueur. (Although he might not approve of a saying that originated with Cromwell.)

Skip forward a few years and #2 seems a lot more like an actual plan than it did before. Thanks to the salary cap and more liberal free agency in the current CBA, it seems almost commonplace that elite-level players with years of prime production come available every offseason. However, you still have to keep your powder dry to take advantage and that happens to be the Oilers' problem.

Just the public list of available talent is tempting and we don't even know who teams like Boston are willing to move to open up cap room.

- The Sedins hit free agency and they're still only 28. The only catch is that you probably have to take them both.

- Bouwmeester is truly an one of a kind free agent as mentioned by speeds over at his site. A legitimate #1 dman at the age of 25 available as free agent? Bonkers.

- Gaborik, Hossa and Havlat are all players with proven track records for driving results and should each be able to provide 4-5 years of quality production. The catch is that you probably have to sign them for 2-3 years beyond their best before date and Gaborik and Havlat have serious injury concerns.

- Lastly, there's Dany Heatley. He's an interesting player, mostly because the Oilers haven't had a player quite like him in a very long time and I'm not even sure what his value would really be, because he's not like the other players I've already listed.

Let's take a look at some of Heatley's selected stats:

The first thing to note is that he's obviously an accurate shooter. Four straight years since the lockout with overall SH% greater than 15%. That is impressive. The second interesting thing is that he has seen his PP icetime drop as a percentage of his total icetime over these four seasons. That doesn't necessarily mean anything but it probably explains why his shooting rate appears to be declining over that same period.

If you check out Vic's timeonice.com site, you can find the underlying stats for Heatley for the past two seasons.

The Corsi is good, but you'd expect that given the starting position of his shifts.
What jumps out at me is the differential in faceoffs starting and ending shifts. I would expect a coach to use a player like Heatley this way, but I'm a little shocked so many shifts ended in his own end. I haven't looked at this before, but is this typical for a serious offensive player like this? At 5v5 Heatley is still shooting the lights out and I'm guessing he's a pretty consistent 13-16% shooter at ES, which is again impressive. However, given the underlying numbers, it's probably safe to assume that Heatley has seen his regular season production as an NHL player driven by favourable starting position and high shooting percentages (and of course some pretty decent linemates). I don't think that's really what the Oilers need right now. They need more players that move the puck to the good end first. The problem with a player like Heatley (besides the fact that they're really really expensive) is that your team has to be pretty good already to make use of him. The Oilers aren't there yet in my opinion, so at least with Heatley maybe it's a good the powder is long gone.

As for the rest of the offseason, I'm hoping for a couple of players that drive possession, but I honestly don't know how Tambellini is going to make anything happen. Adding any one player of quality (that is paid commensurate with his ability) is going to require a minimum of 2-3 deals and that's a hard thing to count on. Two players is probably a pipe dream.

Real Effects and Team Shooting Percentage at Even Strength

'Real Effects' is a term I'm stealing from Bayesian mathematicians. The idea is that if an element of nature is affected by something other than randomness, that it should sustain itself from one independent sample to another.

So if we look at MLB baseball players and their ability to hit home runs, as a percentage of balls that they put in play ... well the Real Effect is enormous. There is a strong association from one set 50 of random baseball games in a season to 50 other random games from the same season. Using Pearson correlation as a convenient way of measuring that relationship, it's around 0.9.

Of course randomness still has it's say, but it's a starting point, and tells that it is possible to separate the ability distribution from the luck distribution for this element of nature. There are no Real Effects for 'players who hit better on natural grass', or 'RH batter vs LH or RH pitcher' (obviously players do a lot better against opposite hand pitchers, just that there is no evidence to suggest that, in the general population, some guys do it better than others). For that matter there is no real effect for the majority of the stats recorded at baseball-reference.com. Though surprisingly there is for most measures of clutchness in baseball.

In this case team I'm looking at Team EV Shooting% for the 08/09 season. Inspired by Jlikens terrific work on the subject over the past season.

Jlikens looked at the distribution of EVshooting% for the 08/09 season, this versus what we would expect the random distribution to look like, and found that there was very little in it. That the overwhelming majority of differences between teams EVshooting%'s was accounted for by luck alone. Surprising stuff, even for the cold hearted folks around this part of the internet.

Of course with just 30 teams in play, it's possible that this distribution occurred by chance. It's like if we were assessing the fairness of a coin flipping contest, where we knew that the coins were weighted differently. If we just looked at one 'season' of coin flipping, it is possible that by chance alone, the spread of results would appear to be the same as that of fair coins. Just because a few of the guys with good coins happened to have a spot of bad luck flipping, and the opposite for some of the guys with poor coins.

So, I thought I would check for real effects with team EVshooting% by upping the sample sizes. For the 08/09 season I randomly selected 19 home games and 19 road games. Then I just took the shooting% for when the score was tied and both goalies were in their nets, this to eliminate the goals from blowout games.

Then, of the remaining 22 home games I randomly selected 19 of them and did the same as above, grabbed the EV goals and EV shots from the tied-game state. Same for the remaining road games.

Then I checked for real effects using Pearson correlation.

Then I did the same thing 1000 times.

And while I was at it I also looked for the real effects of shot ratios and EVsave% while the score was tied.

The script that does it is here, and it will take about a minute to run. And every time it will use different random selections of games, each of these will be listed in the second table, but 1000 samples seems to be enough that the averaged result always ends up about the same:

Real Effects:

EVshooting%: 0.00
EVsave%:     0.14
SF/SA:       0.68

Jlikens is right. Damn, woulda thunk it?

I doubt that this is the case for the NHL in previous eras, especially the 1980s and around 2000. And clearly some players have a better ability to finish, though as MC79hockey has shown us repeatedly usually similar reasoning, that's much smaller than most of us realized intuitively.

And surely this will be the same next season. In fact if we decide right now who are the five best EV goalies in the league, based on EVsave% over the past few years, and eliminate them from next year's test ... then I suspect that we'll see the real effects for goaltending EVsave% fall to almost zero as well. Again, I don't think this was the case 20 years ago, but there are an awful lot of good goalies in the NHL now, and precious few real difference makers in that position.

In conclusion:
1. Possession may not be everything, but in the big picture it's damn close toit. The Oilers need players who drive the terriorial advantage. It would help if Pisani regained his old form as well, there was a time when the play just never seemed to die with the guy. And the forwards that the Oilers do have, they need to be willing to play more below the other team's goal line and finish their shifts more responsibly as well.
2. Unless you're getting an established star goalie, it doesn't make a lot of sense to spend a lot on a second tier guy, either in cap space or trade assets. Because the gap between 2nd tier and third tier appears tiny.
3. Guys coming off of poor percentage years, but with good underlying numbers, and who play a solid game ... these should come at reasonable rates. They should be players that the Oilers buy, not sell. (SEE Reasoner, Stoll and Torres from last summer).

The Impact of Puck Possession and Location on Ice Hockey Strategy

That is the title of this article by Andrew C. Thomas, a must read.

The author followed the Harvard varsity hockey team for a season and recorded some terrific data on possession and zone changes during 5v5 hockey. He then related these to goals scored.

This meshes extremely well with NHL data, but gives a finer look at the 'hows'. In terms of strategy, he found that 'dump and chase' was equivalent to carrying it over the blue line going forward (in terms of expected +/-), and that the same holds true for chipping the puck out of your own end, as opposed to trying to pass/skate it out. This suggests that the ivy league is well coached, and that the players, on the whole, are staying within their roles and abilities (this is my conclusion on the strategy matter, not his).

You can skim over the mathy bits if that's not your thing, as they aren't particularly important. The general idea of still keeping events on the board, even after others have happened ... that's very wise. So if a team gets the puck into the offensive end, and then takes a shot and loses possession, forces the defender into lobbing it back into the neutral zone ... etc, etc ... and a goal is scored 32 seconds later. He would be counting forward from every event to the goal (or to no goal if none were there), as far as 40 seconds. The thinking being that one event (such as getting offensive zone possession) affects the myriad possibilities to come, even if the chain of events doesn't point to that play directly or intuitively.

That's called a Semi-Markov process. Which would make Roger Neilson's stuff from 20 years ago Benjamin Button Semi-Markov (BBSM), where he was looking at the scoring chances and working back through time. The acronym would be better if Brad Pitt's character had been named Benjamin Dutton, but you can't have everything. In fact I would guess that there are only a couple of degrees of separation from Neilson to the person who advised this author on the methodology (the Harvard coach or video coach, maybe? Or an alumni from the professional coaching fraternity?). In any case, by and large he's looking at the right things here. Terrific stuff.

A strict Markov chain is different in that it makes one event alter the nature of the future events, disregarding the events that preceded it. Such as when the score in a hockey game changes from tied to a one goal lead in the early third period ... conventional coaching strategy causes the expected number of total scoring chances to drop from that point forward, and the probability of the trailing team outchancing increases. The score from the first period doesn't affect this a fig, that's the distinction. Or at least that's the way I understand the Markov and Semi-Markov chains. The way of thinking is more important than it's name, in any case.

There is much to be gleaned from this, but the big apple near the bottom of the tree is faceoff data, so I'll grab just it for now. Starting in your own end is a killer; even if you win the draw (much better than losing it, obviously) the prognosis isn't good for the rest of the shift. We all know that I think, but this puts a 'how' with a 'how much'. And the 'how much' is spot on the same for the NHL, or at least for the first half of 07/08, which is all that I checked it against.

Interesting to note also that he acknowledges George Lindsey, an amateur baseball stats pioneer in the 1960s, for his advice. Lindsey's work in baseball is rudimentary by comparison, though it makes me wonder if he would have gone this route with his analysis if he had stuck with his baseball stats hobby. It would have been a monumental task if he had taken it on, baseball is complex.

Scoring Chances: Part VI of Many. The Problem with the PK

Shots metrics like corsi don't work worth a damn on special teams. But now we have scoring chances.

Dennis was sure that the problem with the PK was the skaters. I thought that Roloson was just letting in too many, or shooters were making their shots, luck and all that. It appears that Dennis was completely right.

The goals per scoring chance during even strength hockey was .22.
The goals per scoring chance during the PK was .22.

So like many other checks on Dennis' results, a few of which I listed in Part I, it's eerily consistent.

Roloson's PPsave% was terrible this year, but it looks like it's not his fault at all. The Oilers not only gave up too many shots, as we all knew, but that they gave up a disporportionate amount of scoring chances per shot. And that's on the coaching staff and the skaters, no way around it.

Contrarian goalie is currently revising a post seeing how EVsave% changed from season to season for goalies that changed teams. It's a clever idea. If he accounts for sample size (for both before and after seasons) I suspect he'll find that there is next to nothing in it, but we'll see. BUT, I think that if the same test is applied to PPsave%, we'll see some dramatic shifts.

Scoring Chances: Part V of Many. Home and Away

Much of the banter on Oilers talk radio revolved around the Oilers being a terrible home team and a good road team this season. By eye, this struck me as nonsense. The Oilers played better at home, just got fewer breaks. Of course if you called that thought into a sports radio show you would be roundly mocked and chided, so I didn't.

But Scott has tabbed up the home and away scoring chances for the Oilers this year, and I have the overall league home and away corsi numbers for 07/08 as used in this post last summer.

So, expressed as a percentage of the total, and reflective of the percentage of the territorial advantage, here is how the Oilers did in terms of scoring chances, home and away, in 08/09. The 07/08 leaguewide corsi numbers serve as a benchmark, the average for the league.

And here you are, just click to enlarge:



And the special teams scoring chance numbers were far superior at home. Both the PK and PP. I suspect that this is mostly because an increase in territorial advantage leads to more PPs and fewer PKs for every team. So home teams get a lot more PP opportunities.

So the Oilers were better at home than on the road. And in the right measure. The evidence strongly suggests that the relatively good road record was just luck.

Scoring Chances: Part IV of Many. Anomaly

If you select 38 games from the Oilers season, and then you compare them to 38 other games from the same season, patterns should emerge.

We expect things that are driven by ability to repeat, and using correlation is a convenient way to compare the two sets of numbers. In baseball, this simple repeatability correlation meshes really well with the more complex soultions to the problem of separating luck from ability. And the same should hold true for hockey or any other sport.

If you do this with on-ice EVsave% (using shots directed at net instead of shots on net here, for convenience). There is negligible correlation. 0.02. Nothing there.

So we would expect that the number of scoring chances against, per 100 shots directed at your net ... we'd expect that to not repeat at all. But it does a bit: r = 0.35. Go figure. It's not a big number but it's persistent. 1000 simulations is a lot.

And we would expect that the number of goals against, per 100 scoring chances against ... we'd expect that to not repeat at all. But it does a bit: r = -0.24. Go figure. It's not a big number but it's persistent. And it's negative. Meaning that if you were giving up more goals per scoring chance in one random half of the season (implying that you're giving up higher quality chances) it is likely that the pendulum will swing the other way for you in the other random selection of games. i.e. if a player is giving up more goals per 100 scoring chances in 38 randomly selected games, then there is a better than 50/50 chance that he will give up fewer goals per 100 scoring chances in the other 38 randomly selected games. That doesn't make any sense at all to me.

Use smaller game sets (20 random games vs 20 different random games) and the numbers get smaller but they still persist. r=0.13 for chances per corsi, and r=-0.13 for goals per scoring chance.

Maybe I've just made a mistake in my scripting, but I don't think so. And it probably doesn't matter much to end results. Fine brushstrokes I know. Still, there may be some truth about hockey, something that isn't obvious to the eye, living in this phenomenon.

I'm lost for an explanation.

I suspect that I am about to go on a posting hiatus, hopefully others pick up the scoring chance data from Scott and test some theories.

Scoring Chances: Part III of Many. Scoring Against Minnesota.

For years the Wild goalies have been stopping pucks at a better rate than average. A lot of the credit for this has been given to Jacques Lemaire and his systems play. I suspect that there is something to that, just not as much as most people. Sure, the Wild PK, and especially the fact that they take very few penalties, helps the goalies overall save percentage numbers. They rarely have to kill a 5v3 penalty either.

But at even strength hockey, I think that the goalies deserve mor of the props. Fernandez and Roloson have continued to be very good at stopping pucks at evens since leaving the Twin Cities, and I suspect that Backstrom would also.

On the season as a whole, the Oilers averaged 35.6 scoring chances for every 100 pucks that they shot with malice in the general direction of the other team's goalie. They averaged 65.7 scoring chances for every shot that was on goal (though a great many scoring chances were not recorded as shots on goal).

So if Minnesota really are giving up fewer scoring chances, relative to the number of shots they allow, we should expect the Oilers to have done far worse at generating scoring chances at EV when they played The Wild. Here is how it shook out:

vs League	vs Wild
35.6	35.9
65.7	64.9

Pretty damn similar, no? Yeah, I know it's just six games and it might be coincidence. Still, methinks Backstrom deserves more props than he gets from most hockey fans around the league. And it is unimaginable that the Wild don't track scoring chances themselves, so I expect they knew what they had in Backstrom when they signed him to the long term deal this winter.

The Wild are an interesting team. They have been living off of good goaltending and excellent special teams for a while now, though. If they can land the Sedins this summer, that should send a ripple down the lineup, and they should be very strong in 09/10. They are a lot more fun to watch than they used to be, I think the reputation is larger than the facts in this case. The series against COL last spring was some of the best hockey of the playoffs to my mind.

Possession Is Everything

I think that Mike Babcock is right, possession is everything. Damn close to it at even strength, anyways. I also agree with his thinking that being a "puck possession^(TM)" team has little to do with coaching style, and everything to do with how good your players are.

Scott sent me Dennis' scoring chances for 77 Oiler games this year, cleanly formatted in game by game fashion. So it was fairly easy to drop the scoring chances by game and player into an array, along with the on-ice goals and on-ice shots directed at net (corsi). All the information used in this post is for even strength ice time only.

From there it's simple enough to grab the top 20 skaters by ice time (Stortini being the cutoff point), randomly select 40 games from the season, and see how well EV scoring chances correlates with goals and corsi in those games.

Here I used percentage of the total, it saves buggering about with ice time and seems more relevant in any case. So if, in those 40 games you were on the ice for 20 goals-for and 30 goals against ... that would be a goals rating of 40%. i.e. 40% of the goals that happened were for your team. Same for scoring chances and corsi.

I wrote a script to randomly select 40 games from the season and calculate the correlation. And then to do the same 1000 more times. And as shown in the chart above, after 40 random Oiler games this past season; the correlation of scoring chances to corsi averages .84, and the correlation to goals averages .59. Both strong relationships.

And then I repeated the excercise for 10 game samples, 20, 30, 50 etc.

The idea is that the more games you're looking at, the more luck washes out. And you can see that over a small batch of games the player's scoring chance rates mesh reasonably well with results (goals) for these 20 Oiler players as a group. But as the sample of games grows larger, near the 77 total, the relationship becomes overwhelming and obvious. And if the season were 40 games longer there is every reason to think that the correlation would grow even stronger, even though there isn't much room to grow at that point.

And corsi, our best guess at territorial advantage using readily available stats, it becomes remarkably similar to scoring chances given enough games of data.

In this season, the on-ice shooting% was spread fairly evenly across the board, so the relationship of scoring chances to goals is stronger than it will probably be most years.

Bottom Line: Players that drive possession at EV drive results at EV. Maybe not the next game the Oilers play, or the next dozen, but eventually. It's unstoppable, ability trumps luck eventually, you just have to be patient.