April 15, 2014


The People Pushing the NHL Into the Advanced Stats Era (ERIC TULSKY, 4/06/14, 538)

With 17:25 left to go in the first period of a December National Hockey League game between the Philadelphia Flyers and the Edmonton Oilers, the Oilers gathered the puck in their defensive end and passed it ahead to Jordan Eberle, who was headed up the left side of the ice. The Flyers' defensemen -- Kimmo Timonen and Braydon Coburn -- were well positioned, but Eberle decided to challenge them. He cut diagonally across the ice towards Timonen, drove wide to the far boards, put on a burst of speed and beat Timonen to enter the offensive zone.

Somewhere, Jessica Schmidt was watching. She has spent the last two seasons tracking each entry into the offensive zone with a spreadsheet open in front of her. A 26-year-old diehard hockey fan, she had read some articles I wrote about the Flyers' zone entries in the 2011-12 season and the usefulness of zone entries in assessing a team's performance. When the Flyers missed the playoffs in 2013, she wanted to know what had gone wrong and volunteered to try recording the zone entries herself.

That information doesn't come easily, however. Schmidt estimates that tracking a game takes her about 90 minutes, which means that it would take an incredible amount of dedication and effort from several people to collect a year's worth of data for a handful of teams. It would take a whole platoon of volunteers to track zone entries for every NHL game, and even then they would be capturing only specific pieces of select key moments. An NBA analyst wouldn't need someone like Schmidt to put in hundreds of hours tracking zone entries; that sort of information -- and much more -- is easily gleaned from the NBA's automated video tracking system, SportVu. But hockey lacks the position-tracking systems that many other sports use, even though there are hugely important lessons their data can teach.

Instead, it has people like Schmidt. As Eberle drove around Timonen into the offensive zone, Schmidt made a note in her spreadsheet: "1 17:22 C Opp 44." Translation: in the first period, with 17:22 left, there was a carry-in (C) by the Flyers' opponent defended by the Flyers' No. 44, Timonen.

That last part -- who defended the play -- was a new wrinkle Schmidt and I added this year. Previous analysis had given us important insight into the performance of the puck-carrier, but assessment of the other nine skaters on the ice relied largely on inference. This year, I asked Schmidt to include some off-puck information -- things like which player retrieved the puck when the Flyers dumped it in, or who had primary defensive responsibility on the opponent's entry.

Tracking by Schmidt and others has helped explain that a team's entry into the offensive zone has a big impact on its shot differential. Carrying the puck into the offensive zone leads to more than twice as many shots and goals as a dump-and-chase play does, even after removing plays like odd-man rushes and dump-ins that are made just to buy time for a line change. These results have even made an impact on strategy.

Posted by at April 15, 2014 4:13 AM

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