PDO is basically a proxy for luck in hockey. The number comes from adding a player’s on-ice shooting percentage with their on-ice save percentage. For example, a player may look better than he actually is because his goalie is saving absolutely everything whenever he’s on the ice, with the chance it all comes crashing down rather abruptly. (This happened to the Flames’ third defensive pairing late in the season.)
xPDO, meanwhile is a player’s expected PDO. The general rule of thumb has been that a PDO of 100 means the player was neither lucky nor unlucky, and what should have happened happened; by adding the player’s expected Fenwick shooting percentage to his expected Fenwick save percentage, it gets narrowed down to an individual focus.
Is it perfect? Does it mean a player with a low PDO is due to be better next season? Not necessarily – but it does hint that maybe their previous season didn’t go as well as could have been reasonably expected, and it wasn’t entirely their fault.
Here’s the Flames’ PDO and xPDO for 2016-17, via Corsica:
There is, of course, variance amongst everyone’s PDO and xPDO, but some have greater disparities than others. If the difference is less than one percentile, then we can assume that player’s “luck” swung neither good nor bad for him, and his season was an accurate reflection of what it should have been.
In that case, eight Flames fit that bill, and mostly top players at that: Backlund, Ferland, Dougie Hamilton, Frolik, Gaudreau, and Monahan, not to mention Stajan and Bouma. Monahan comes the closest to trending towards lucky, though, while players like Hathaway and Tkachuk are only just over.
Players who had lucky seasons could be considered to have disparities of +1 or more. Engelland, Brouwer, and Bartkowski all fit this bill; not exactly a great sign, as they had overall suboptimal play this season, and that was with the fates smiling on them a little.
Giordano, Versteeg, and Stone offer the bigger cause for caution. That isn’t to say they’ll be bad in 2017-18 – we have no way of knowing for sure until the games are played – but merely to be careful with expectations for them. Stone has the greatest disparity of everyone, and does bring up legitimate concern that the trade deadline acquisition was more lucky than properly suited for a top four role.
Then there are players who had a greater negative disparity, or were unlucky: Wideman, Brodie, Freddie Hamilton, Chiasson, Kulak, and Bennett. The only name who seems out of place when considering an unlucky season is Chiasson’s; otherwise, everyone else seems to fit the bill – especially players like Kulak and Bennett, young guys who should be a part of this team’s future but either didn’t get a proper chance (Kulak) or who had a difficult time having things go right (Bennett). This is where you hope the numbers are right, as they do point towards those players being better than they were this past season – and for Brodie and Bennett in particular, that is very much the expectation.
If everyone regressed, then Brodie’s possible improvement could cancel out Giordano’s potential decline, and the same goes for Bennett and Versteeg. That said, some players will undoubtedly have a lucky 2017-18, and some will have an unlucky one – and all we can really do with these numbers is try to make an educated guess as to who has more to offer, and who might have a little less.
For the most part, I’d say they match up well with most preconceived notions of each player’s season.