"It is exceedingly difficult to make predictions, particularly about the future."
Predictions are a funny business. It's not difficult to make simple predictions based on logic and mathematical principle and hit a number of them on the button. Move away from the simple, towards the absurd and predictions become more difficult. Leave the realm of numbers completely and predictions become a Sisyphean endeavor, though with experience, sometimes accuracy is unavoidable. In hockey analytics, one area of success has been using underlying stats to predict future performance, both at the team level and individual level. The application of some very simple formulas in combination with some even simpler comparisons can determine those Oilers who will rebound in 2011-2012 and those who will fall.
First some definitions of the stats used in this post. PDO, like an element on the periodic table, was discovered by and named for PDO, a frequent and bright commenter in the Oilogosphere. It was developed by Vic Ferrari at Irreverent Oiler Fans. Behind The Net Hockey has a simple definition for PDO:
It is just Save Percentage plus Shooting Percentage [more precisely: PDO=1000*(G/SF+SV/SA)]. What's interesting about it is that it trends very heavily - at the individual level or the team level - to its mean of 1000. But it is possible to assemble a team that plays above 1000.
MC79hockey did a wonderful job of breaking out the number in a series of posts, here. PDO can be found on the Corsi report at www.behindthenet.ca.
On Ice Sh % is the even strength team shooting percentage while the player is on the ice. On Ice Sh % can also be found on the Corsi report at www.behindthenet.ca. On Ice Sv % is the even strength team save percentage while the player is on the ice, and can once again be found on the Corsi report at www.behindthenet.ca.
How is this information instructive? Tyler and Gabe showed us that, except for the very best, PDO will cluster around 1000. We also know that over time shooters will shoot at their established rate and fall off as they age. Like a simple stock trading program, I set the spreadsheet up so that the top five values of concern in each category are in red and the top five values of interest in each category are in green. A bunch of red cells mean that it's likely that the player in question will see reversion and a bunch of green cells mean it's likely that the player in question will see improvement.
|Player||On Ice Sh%||On Ice Sv%||PDO||10-11 Sh%||Career Sh%||Difference|
Expected counting numbers increase
- For the second consecutive year, Cogliano's shooting percentage was well below his career average. Last year his 7.2% shooting percentage greatly reduced his career average and this year's 8.5% wasn't much better. Is he closer to the 16.8% shooter from his first two years in the league or is he closer to the 7.8% shooter he's been over the last two years?
Expected counting numbers decrease
Underlying stats expected to improve
- Linus Omark leads the way here. He was a -15 in 51 games at even strength, but with an average PDO, Omark would have been -1 at even strength. Both his on-ice shooting percentage and on-ice save percentage were among the worst on the team last season.
- Jeff Petry was -11 in 35 games at even strength, but a league-average goaltender could have bailed him out. With a .920 even strength save percentage, he would have been -1. With an 8% on-ice on shooting percentage, he would've been +1.
Underlying stats expected to decline
Ryan Whitney - With his on-ice shooting percentage and his on-ice save percentage set to fall, his PDO will revert back towards 1000 and bring his traditional +/- with it.
If Ryan Whitney was healthy and without an injury history, his trade value would never be higher. Of course, suggesting a Whitney trade to the casual fan would be looked upon as lunacy. It will be interesting to see just how far Linus Omark bounces back as his numbers settle in where they belong. There's a real possibility that he will amaze a number of observers with his point totals next year. With moderate power play minutes next season, I wouldn't be surprised to see Omark average .6 points per game and clock in at 50-55 points in 2011-2012.