More so than most sports, hockey is a game that requires luck to succeed. This, understandably, makes analysis more difficult to construct than, say, baseball: where most situations are extremely quantifiable, straight-forward and easily digestible.
But what if we could quantify luck in hockey? Thanks to PDO, we can.
PDO, at a team-wide scale, adds shooting percentage and save percentage during even strength action. For example, if a team’s EV SV% is .930 and it’s EV S% is .010, its PDO would be 1001.
Since every shot on net leads to a save or a goal, the NHL-wide PDO is always 1. And while disparity in talent will always result in varying PDOs across the league, history tells us that teams’ PDOs normalize back toward 1 over large sample sizes — e.g. an 82-game season.
Right now, the highest PDO in the league belongs to the Bruins (1052) and the lowest belongs to the Rangers (926). That’s a difference of 126.
To provide some perspective, here are the differences between the best and worst PDOs over the last several (full) seasons:
As you can see, the imbalance shrinks considerably as time wears on. Luck, good or bad, rarely lasts.
Hawercuk over at Arctic Ice Hockey did a good job explaining the power of this statistic:
Add [shooting percentage] and [save percentage], and you get a statistic that is almost 100% luck. How can this be? Surely there are players or lines who are higher-percentage finishers than others and can also play adequate defense? I’m not saying there aren’t but for the vast majority of NHL regulars, a high PDO in one season comes crashing down the next. And many players with high one-ice shooting percentages get them by cheating offensively, which leaves them susceptible to higher-percentage opportunities against them at the other end of the ice.
It’s important to point out that a team’s PDO doesn’t reflect how good it is. Take the 2007-08 Thrashers: in many numerical categories they were one of the worst teams this millennium; however, their five-on-five PDO that year was 999 — almost exactly even.
So how can we relate this to the Predators? Well, thus far in 2013-14 they’ve been a pretty unlucky team, and if you’ve watched them play you don’t need any fancy numbers to back up that sentiment. While Nashville’s goals for average is currently worse than last year, its offense is operating at a higher level than it did in 2012-13, as evident by its improved possession stats.
“Yeah, we’ve definitely been unlucky,” Patric Hornqvist said a few weeks ago. “The only thing we can do is keep pushing the way we have, and keep working in the system we have.”
Through Thursday’s action, the Preds sit 26th in the NHL in five-on-five PDO at 0.973. This is not surprising, but at the same time it’s bound to get better.
Via ExtraSkater.com, here’s how the whole league looks at the moment:
|2||Toronto Maple Leafs||14||104.1|
|4||St. Louis Blues||10||103.6|
|6||San Jose Sharks||13||102.9|
|15||Columbus Blue Jackets||11||99.7|
|17||Tampa Bay Lightning||12||99.3|
|18||Detroit Red Wings||13||99.2|
|19||New York Islanders||12||99.2|
|28||Los Angeles Kings||14||97.2|
|29||New Jersey Devils||12||96.3|
|30||New York Rangers||12||94.2|
Hockeyanalysis.com and behindthenet.ca began calculating PDO in 2007-08, and no team between then and 2011-12 finished a season with a PDO lower than Nashville’s current figure. (Last year’s data isn’t worth analyzing here given lack of data the 48-game schedule provides).
If the Predators can continue to play at the rate they have, they’re luck — and thus winning percentage — should experience a nice boost.