The top five teams experienced what stats people sometimes call “PDO benders,” where they scored and won games at a rate wildly out of whack with their shot share (SF%). For example, the 2015-16 Panthers shocked the hockey world by winning the Atlantic division. They scored 56% of the goals at 5v5 and won 47 games despite being about even in terms of shots, in large part because of an inflated 102.1 PDO. The next season, despite only playing slightly worse, their percentages regressed and then some, leaving them below .500 and costing Gerard Gallant his job. PDO told us that they were not as good a team as they seemed in 2015-16, and not as bad as they seemed in 2016-17. The bottom four teams prove that the same can be true in reverse; the 2014-15 Coyotes had abysmal percentage luck and rode it all the way to a third overall pick. The next season they were actually worse in terms of shot share, but because their PDO regressed upwards they finished just below .500.
The traditional line with PDO is that it will “regress to the mean”, i.e. 100. But as we saw above, there is a skill component involved, even if it is slight. Based on the trendlines above, I calculated using a simple linear regression what an “expected” year two percentage performance might look like for each team-level save percentage, shooting percentage, and PDO:
