Is There An 'Injury Epidemic' Because Of The NHL's Trapezoid Rule?

Conventional wisdom says that there's been an increase in injuries since the implementation of the NHL's trapezoid rule. Some have even called it an 'epidemic.' SB Nation's Derek Zona, meanwhile, calls these claims 'intellectually dishonest.'

Coming out of the 2005-2006 season, the NHL, by recommendation of the Competition Committee chose to implement a restricted area, in the form of a trapezoid, behind the net in order to prevent the goalie from playing dump-ins and clear the defensive zone. 

From Rule 1.8 of the NHL rulebook:

Goalkeeper’s Restricted Area - A restricted trapezoid-shaped area behind the goal will be laid out as follows: Five feet (5') outside of each goal crease (six feet (6') from each goal post), a two-inch (2") red line shall be painted extending from the goal line to a point on the end of the rink ten feet (10') from the goal crease (eleven feet (11') from the goal post) and continuing vertically up the kick plate.

The punishment prescribed for a restricted area infraction, a two minute minor penalty, was implemented in Rule 28.8:

Restricted Area – A goalkeeper shall not play the puck outside of the designated area behind the net. This area shall be defined by lines that begin six feet (6’) from either goal post and extend diagonally to points twenty-eight feet (28’) apart at the end boards. Should the goalkeeper play the puck outside of the designated area behind the goal line, a minor penalty for delay of game shall be imposed. The determining factor shall be the position of the puck. The minor penalty will not be assessed when a goalkeeper plays the puck while maintaining skate contact with his goal crease.

Since the implementation of the rule, there have been calls from the media, fans and team executives in the NHL to repeal the trapezoid.  Recently, those who want to repeal the rule have centered their arguments around defensive injuries -- the reasoning goes that because defensemen are chasing the puck with their back to the play, they are exposed to aggressive forecheckers and have suffered bigger hits more often, leading to injury.

At the head of the media pack calling for a repeal of the Trapezoid Rule has been Don Cherry.  Cherry has railed against the rule in his weekly "Coach's Corner" segment for CBC. Emphasis below is mine.

Cherry specifically targeted the interference crackdown instituted by the NHL after the lockout in 2004-05 and a rule limiting where goalies can handle the puck — the "trapezoid" rule — as serious causes of the injury epidemic.

He said those rules make it more dangerous for defencemen to play the puck in their own end. "They cannot dump the puck in and have forwards like [Todd] Bertuzzi coming in [and] nailing [defencemen]," Cherry said back in 2004.

The Trapezoid Rule was on the agenda for the the NHL General Manager's meetings in November, and the rule was left untouched.  Carolina Hurricanes President and General Manager Jim Rutherford is one executive that believes the rule has increased injuries league-wide:

"I'm a little bit surprised that more guys didn't want to take a closer look at it.  But I'm sure that when a few more defensemen get hurt during the year we will talk about it at another meeting."

Nashville Predators General Manager David Poile doesn't believe that the rule is playing a part in injuries:

"We did a lot of thinking about those rules.  We want more scoring and we don't think there has been a lot of hits just because of the trapezoid."

Even though bloggers have brought about a mini-revolution in injury and injury impact analysis, the nebulous nature of NHL injury reports make direct examination of these claims extremely difficult.  However, if folks like Cherry and Rutherford are correct, that the rule is causing an increase in injuries to defensemen, the most obvious effect would be in games played by defensemen, though I'm sure Cherry would have no use for analysis that uses stupid things like numbers

Below is a chart breaking out games played by defensemen for the four seasons prior to the implementation of the Trapezoid Rule and the four seasons since.  

Def. Games  0-9  10-19  20-29  30-39  40-49  50-59  60-69  70-79 > 79
2001-2005 245 157 102 89 84 129 149 231 168
2006-2009 217 134 107 70 99 109 164 206 195

 

In the four-year period since the rule was implemented, 30 NHL teams have used 53 less defensemen compared to the period prior, a statistically insignificant three percent difference.  The numbers above show that since the rule was implemented, there have been more defensemen playing more than 79 and 59 games per season.

There is a differential of 53 games between the two observed periods, so I've also broken this down by percentage:

Def. Games  0-9  10-19  20-29  30-39  40-49  50-59  60-69  70-79 > 79
2001-2005 18.09% 11.60% 7.53% 6.57% 6.20% 9.53% 11.00% 17.06% 12.41%
2006-2009 16.68% 10.30% 8.22% 5.38% 7.61% 8.38% 12.61% 15.83% 14.99%

 

Defensemen have played slightly more (though still statistically insignificant) games per season since the Trapezoid Rule was implemented.  The calls for change based on injuries may have anecdotal backing, but there is no "injury epidemic" as Don Cherry and CBC put it.  The rule may still deserve a second and third look, and it just might deserve to be eliminated, but to put the rule to the test because of injuries would be intellectually dishonest.

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