What Can PDO Tell us About the Toronto Maple Leafs?

Since I looked into Pythagorean expectation recently, I thought I would look at another advanced stat, PDO, to see if it can tell us anything about the Toronto Maple Leafs.

PDO is simply the addition of a team’s shooting percentage and save percentage at even strength, the sum of which should equal one (or 1,000 if you convert the percentages to whole numbers and multiply by 10 as I do here).  The stat was developed by advanced stats guru Vic Ferrari.

So why is PDO important?  Tyler Delow at mc79hockey does a good job explaining how sustaining an extremely high or low PDO over an entire season is rare and most team regress to the mean.  The point being that shooting percentage and save percentage are partially products of luck.

This might come as a shock to most people, but it is true.  Goals are a product of shots and shot quality, not necessarily the skills of the shooter or the goalie. I am convinced of this for shooting percentage, but with save percentage I still think this has a lot to do with the guy between the pipes.

PDO is also a very good measure to evaluate players, as a player’s on-ice PDO gives you a good idea whether he has been lucky or unlucky.

The table below gives a breakdown of each team’s shooting percentage, save percentage and PDO.

The New Jersey Devils of 2010-11 versus the New Jersey Devils of 2011-12 show the effect of what PDO can do to a team.

In 2010-11 the Devils had a league-low PDO of 978.  They actually outshot their opponents at even strength but they had a league-worst shooting percentage of 6.8 percent.  Fast forward one year and the Devils avoided some of the bad luck they encountered the previous season and ended with an improved PDO of 994.

This was on the strength of an 8.5 shooting percentage.  They also went from 24th place overall to eight place in the league standings.

Year over year adjustments are not always the case, especially when you look at a team’s save percentage. Teams like the Vancouver Canucks and Boston Bruins have been consistently at the top of the PDO rankings the past few seasons and this is mainly due to upper echelon save percentage numbers. Considering the guys they have in net, that is understandable.

What you will tend to see is a reversion in a team’s shooting percentage.  Where this stat becomes very interesting is during the season.  Teams that have unusually high or unusually low PDO stats early in the year almost always revert to the mean of 1,000, or they at least make an adjustment in that direction.

A great example of the effect of luck on shooting percentage is the 2011-12 Stanley Cup Champion Los Angeles Kings.  The Kings had a league-worst shooting percentage during the regular season of 6.4.  In the playoffs, with the same players, they had the third highest shooting percentage at 9.3.

Clearly a team that had very good possession statistics during the regular season could not sustain an extremely low shooting percentage for much longer.  They started to get the bounces in their favor rather than against and this helped them achieve the ultimate goal.

The Maple Leafs ended the 2011-12 season with the 27th ranked save percentage and the 10th ranked shooting percentage, giving them a PDO of 992, which put them 26th in that statistic.

In terms of shooting percentage, the Maple Leafs are slightly above the league average, so they may be in for a small correction next season.  The bigger question is whether the Leafs’ poor save percentage can be attributed to bad luck or if it is solely a factor of the guys between the pipes.  The answer is likely a combination of both.

Clearly the Maple Leafs have had their issues in goal and it is the prime reason their PDO score has been less than 1,000 for five years running.  Having all the bounces go against you likely won’t happen for five seasons in a row.  Thus some improved play in goal by whoever next year’s goalies might be and having a few extra bounces go their way should help the Maple Leafs get their PDO up to or above 1,000, which can only help them in their hunt for the playoffs.

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