February 20 2013 01:26PM
"PDO", which doesn't stand for anything, can explain how hockey teams performed in a short amount of time.
It is the simple addition of a team's even strength shooting percentage and a team's even strength save percentage. Over the long run, it's been observed that the "PDO number" comes closer to 1.
It is also a very counter-intuitive concept, since it assumes that the value of every shot is equal, that teams have equally-good shooters and goaltenders. That said, teams that start the season with high PDOs tend to finish the season with lower PDOs. As of Monday morning, there were nine teams that had their goaltenders combine for .930 even strength save percentages or higher. After 82 games last season, only two teams managed that.
The overall worry here is that the Toronto Maple Leafs, as of Monday, had the third highest PDO in the National Hockey League. Their shooting percentage was 10.1% and their save percentage was .938. Add those two numbers together and you get 1.039. The highest that Randy Carlyle's Anaheim teams finished under him since we've had PDO data is 1.011.
I won't bug you much with the math behind regression, but I thought to bring out some real-world applications. I dug back through the last three seasons to find the teams with the highest PDO numbers after the first month:
|Season||Team||Shooting %||Save %||PDO|
There's a scattering of teams there in quality. The 2011 Boston Bruins won the Stanley Cup, and the 2010 Edmonton Oilers ended up in 30th and got the first overall pick. The 2010 Washington Capitals won the Presidents' Trophy, but got beaten in the first round. The 2011 Dallas Stars and the 2010 Colorado Avalanche became poster boys for regression: both teams had a strong start, and the Stars fell out of the playoffs on the last day. The Avalanche still managed to finish 8th.
Since the Leafs have played 17 games, here are those teams' records after the first 17 games:
It's funny how similar PDOs can have such different effects on some teams. The Oilers had better shooting and save luck than six other teams here, but they were .500 after 17 games. The point of this is that a high PDO can make good teams look great, and bad teams look good.
Here are those same teams' records from Games 18 through 48 in that same season:
Only the 2011 Stars and 2012 New York Rangers improved their records. The Stars implosion would come later in the season, but the purpose of today's post is to see whether the Leafs have banked enough wins with an elevated team save percentage to make the playoffs. It's certainly possible: they have 31 games left and are three points clear of the 8th-place team. Last season with 31 to go, they were just two up of the next team, but the Capitals, who were chasing them, held a game in hand.
Around that time last winter I wrote a post about the Leafs' playoff fortunes, saying "Should the shooting [percentage] falter, I'm not convinced the team has the defence or goaltending to stay in a playoff spot."
A commenter named 'advancedstatsareafraud', a harbinger if there ever was one, wrote the following under that post:
When the leafs, with excessive PDO and way too low Fenwick, make the playoff - then finally people will come to realize that advanced stats are a complete fraud. The leafs laugh and are better then all this "regression to mean" talk.
I couldn't help but remember that comment when I saw 'leaferfan' post something similar on the post at NHLNumbers this week that showed the Leafs' in third place in the NHL in PDO:
I dont' care about this PDO nonsense. Mclaren and Orr will pull the leafs into the playoffs kicking in screaming with a few good punches along the way.
The bad news is that the Leafs are currently outplaying their means. They're 5-2 in one-goal games and 5-5 in contests decided by two goals or more. There's every indication that one shot or save that goes the wrong way could result in changing a game.
Anyway, total up the above teams' records and look at the key: points per 48 games:
It doesn't look like much of a drop considering nearly half the season has been played already. Over 82 the difference would be much greater, but it's still enough to change the Leafs' overall fortune. Toronto are at 10-7-0, on pace for 56.5 points over 48 games. It's expected that something around that number could be the number to get into the playoffs. Right now, I wouldn't bet money on the Leafs' maintaining their current level of winning, based on what has happened to teams in the past. They're right on the cusp where the four or five points that could be explained by PDO regression to the mean could put them on the outside-looking-in.
Right now, the Leafs are relying on out-scoring the opposition and not out-shooting them. While they've generally had more scoring chances than the opposition, it's been found that over time, scoring chances sync up with shot differential statistics. Right now the Leafs are benefitting from some good puck luck, and that's driving their record moreso than coaching, leadership, size or being an improved hockey team.
There is still room to improve. There is an unsigned, play-driving centreman ripe for a trade. The Leafs' best two-way centreman has played below 15 minutes in five of the last six contests. Maple Leafs defenceman Jake Gardiner is playing with the Marlies, and Marlies defenceman Korbinian Holzer is playing with the Maple Leafs. Reliable face-off and defensive centreman David Steckel is a healthy scratch nearly every game. Even with the winning record, the Leafs' underlying performance numbers paint a chilly picture.
So, no, if the Leafs keep doing what they're doing, I don't expect them to win 10 out of 17 games to make the playoffs. Teams over a 1.030 PDO in the last three seasons have had an observed drop in points per 48 games of seven. That would put Toronto on a 52-point pace for the remainder of this season with all the wins they have banked. Would that be enough to make the playoffs? Not unless the team improves.