Follow the numbers (and Patrick Roy): Pull your goalies, NHL coaches

Rob McKenzie applauds Patrick Roy for his bold use of the goalie-pull tactic in ice hockey, and explains why more coaches should more aggressively use it.

Patrick Roy and the Colorado Avalanche are have 55 points and 22 wins from 54 games played this year in the NHL. Doug Pensinger / Getty Images / AFP

Statistics show it, common sense suggests it and Patrick Roy proves it: teams that want to win should pull their goalie more than they do now.

Pulling the goalie in favour of an extra skater is hockey’s great risk-reward exercise, a parallel to fourth-and-long in American football. It increases the trailing team’s chance of scoring, but increases the leading team’s chance to a greater degree. Yet the trailing team can turn defeat into victory; for the leading team, victory merely becomes victory by a greater margin.

The Colorado Avalanche, with Roy as their coach, are masters at this. In January and February the team had an unheard-of streak in which pulling the goalie led to a Colorado goal in three successive games, and four in five.

It was more than a fluke. Roy has long been aggressive in pulling the goalie, notably in last year's play-offs. His team does it often enough that what is desperation time for others is business time for them.

Colorado’s Tyson Barrie, after scoring against Dallas with 20 seconds left and an extra skater on the ice said: “It’s big for us to know that [if] we are down a goal, we do need a big goal, that we’re confident we can get it done. Guys don’t squeeze their sticks too tight.”

Research has shown for years that coaches should mimic Roy’s approach.

As far back as 1989, Philadelphia-based professors Robert Nydick and Howard Weiss reported that optimal times for pulling the goalie ranged from three minutes, 25 seconds, for a strong offensive team, to 1:19 for a weak one. “Under any reasonable set of assumptions,” they wrote, “hockey coaches wait too long before pulling the goalie.”

More recently, two federally funded Canadian professors analysed a variety of game situations and concluded that a more aggressive approach would be worth two to three points in the standings at year’s end. (Or more: during Roy’s hot streak, his tactics added six points to Colorado’s column.)

The two Canadians, who parsed the statistics of every 2007/08 game, noted that pulling the goalie typically happened with a minute left in a one-goal game and 90 seconds in a two-goal game: suggesting that strategy had little evolved since 1989, when the norm, Nydick and Weiss generalised then, was to pull with a minute left.

An analysis of NHL games in January shows that coaches, perhaps influenced by Roy, are finally wising up. Teams pulled the goalie in 105 games. In 59 of those games, they did so with more than 90 seconds left. That included 29 times with more than two minutes left, six times with more than three minutes left, once with more than four minutes left and once with more than five minutes left (that was Columbus, down four goals to Arizona).

An intriguing idea derived from the numbers is that if you are losing in the third period, and the other team takes a penalty, you should press the advantage by pulling your goalie.

According to the Canadian research, in a normal six-on-five situation after pulling the goalie, the team that pulled scores every 8.5 minutes. But switch that to six-on-four (team with a man advantage also pulls the goalie), and the scoring rate rises to once every 5.5 minutes.

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