Shooting performance occurs in a slightly larger spread, but there are still bounds to it. 939 (5v5) over a season the vast majority of the time, even accounting for goalies who don’t play much. Goaltender performance is notoriously clustered across the league, for instance. The second is that there’s a relatively narrow band of performance in these statistics. So as accurate as Stamkos may be, his on-ice shooting percentage will not be that high. And Stamkos has very, very little control over his goalie’s save percentage.
Steven Stamkos may be able to score on 12% or more of all the shots he takes, but the 4 other guys he skates with aren’t. Individual players have very little ability to consistently affect the shooting percentages of their linemates. The first is that this is on-ice performance, not individual performance. However, two things are acting on PDO to bring it into line. What about talent? Some guys are better shooters than others. In the meantime, you know that randomness in terms of the timing of goals both for and against has had a strong effect on Forsberg’s first five games. But, like flipping a coin, it will get closer and closer over time. But just like flipping a coin, it may take 3 more games it may take 20 more games it may take more games than there are in a season. As he adds data, his shooting and save percentages will regress towards the league mean of 100. The same is true of Filip Forsberg’s season. In the meantime, that 80% heads rate tells you that randomness has had a strong effect on the outcomes you got in those first five flips. But it will get closer and closer over time. It may take 3 more flips to reach exactly 50% (all tails) it may take 20 more flips it may take 1000 more flips. You understand that if you keep flipping that coin, if you add data, it will–whether gradually or precipitously–move closer and closer to 50%.
You know that the average will be 50% heads, not 80%. Basically, PDO takes advantage of a feature of how the numbers fall to describe a particular slice of the season.Īn analogy: Imagine that you flip a coin 5 times and get HHHTH. The value of PDO lies in it’s ability to show how far away one particular player or team’s experience is from the average. In fact, if they did–if everyone’s on-ice shooting and save percentages were always 100–PDO wouldn’t work. How can the ability of his linemates to score affect the ability of his goaltenders to make saves? The average, then, is mathematically defined.īut, you say, there’s no reason for Filip Forsberg’s on-ice save and shooting percentage to equal 100.
#Pdo meaning plus#
Thus league save percentage plus league shooting percentage is always and invariably 100. There aren’t any shots in the league that are not goals or saves. Every shot in the league is either a goal or a save. This is called regression to the mean, and the NHL (or any hockey league), the mean is exactly 100. The greater the distance from 100, the more likely there will be a change.
He and his linemates are scoring on 14.7% of the shots they get on goal. Forsberg has yet to be on ice for an 5v5 goal against. It’s the 8th highest PDO in the league among skaters with 50 or more minutes at 5v5. For instance, right now, 5 games into the season, Nashville Predator Filip Forsberg has a PDO of 114.7. To interpret a PDO number, you look at the distance from 100. Obviously, for a team, on-ice numbers are all numbers. It works a bit better that way because power plays and penalty kills have different levels of scoring than 5v5 play and every player/team sees a different mix of PP/PK and 5v5 time. Most of the time we use 5v5 numbers but you don’t have to. To arrive at a PDO number, you add on-ice save percentage to on-ice shooting percentage. It does that very easily and very efficiently. What PDO does–the only thing that PDO does–is highlight those players or teams who are getting better or worse results than they ought to be given how skilled they are. It just doesn’t do anything more than that. None of those have worked because PDO actually does what it’s supposed to do. And whole screeds have been written to try to take it down from the base out. It’s a weird little stat, not very commonsensical. People say a lot of stuff about PDO and there are a lot of ways in which it gets attacked.