Thursday, January 05, 2017

Columbus Blue Jackets Seek to Tie NHL Record for Longest Winning Streak

Tonight, in the nation's capital, the Columbus Blue Jackets will try to tie the NHL record of 17 straight wins, held by the 1992-93 Pittsburgh Penguins. Here's a chronicle of how the team's 16 wins have unfolded. Many articles have appeared on the Blue Jackets' streak, from analytic (here, here, and here), and even Bayesian statistical perspectives. I was interviewed in this SB Nation article.

Two main issues stand out to me. One, which the SB Nation writer discussed with me but didn't make it into the article, is the likelihood of a team with the Blue Jackets', shall we say, non-illustrious history going on such a long winning streak. As I wrote in my book Hot Hand, "many of the most famous streaks... have been compiled by athletes and teams who are among the all-time greats in their respective sports" (p. 5). Examples cited include Kobe Bryant, Joe DiMaggio, and Tiger Woods. As the late Harvard paleontologist Stephen Jay Gould once wrote, "Long streaks always are, and must be, a matter of extraordinary luck imposed upon great skill."

The Blue Jackets hardly seem to be the kind of winning franchise, upon which only a little luck would have to be added to produce a long string of victories. Columbus has made only two playoff appearances in the 16 years of franchise history, most recently in 2013-14. At the risk of overstatement, a Blue Jackets' winning streak would be like hearing that a run of 50 consecutive made free throws belonged to Shaq O'Neal rather than Steph Curry.*

The second issue, pertaining to on-the-rink statistics, involves shots on goal. Because goals are rare in hockey, analysts typically focus instead on teams' shot-on-goal totals, which turn out to be a good measure of puck possession (see the new book Stat Shot: The Ultimate Guide to Hockey Analytics, by Rob Vollman and colleagues, for further discussion).

As shown here, in games before the streak, Columbus and its opponents were each taking roughly 50% of the shots (see the columns marked Corsi, Fenwick, and Shots For). During the streak, in contrast, the Blue Jackets have around 54% of the shots in their games and their opponents, 46%. Aggregate shot totals can be misleading, however, because of score effects, the phenomenon of a trailing team bombarding the opposing net with desperation shots in an attempt to get back in the game.

I created the following graphic to take game context into account. Using a puck image for each game during the Columbus winning streak, I plotted the Blue Jackets' deficit or lead on the scoreboard on the x-axis (from losing by 2 to winning by 4). On the y-axis, we see differences between the Blue Jackets' and opponents' actual numbers of third-period shots (which may be more intuitive to grasp than the percentage of total shots attributable to each team). The puck in the upper-left corner of the graph, for example, represents the Blue Jackets' December 3 game at Arizona, the third game in Columbus's streak. The Jackets trailed 2-1 after two periods (the only game during the streak in which they entered the third period trailing), but in a feverish attempt to tie the game (which Columbus did with 2:16 remaining), outshot the Coyotes 23-4 in the third (+19). Columbus eventually won 3-2 via shootout.

If a game is close (i.e., tied or within one goal either way) heading into the third period, we should find Columbus dominating the shots-on-goal totals in the third period during the winning streak. If the Blue Jackets are relatively comfortably ahead, on the other hand, we would expect their opponents to be dominating the shots. This is exactly what we find.

For those with some statistical training, the correlation between size of Columbus's lead on the scoreboard (with a deficit scored with a negative sign) and their edge or deficit in third-period shots was a statistically significant (r = -.58; see blade of the hockey stick in the graphic). The less favorable the Blue Jackets' situation after two periods (trailing or tied), the more they outshot their opponents.

So, if you're a Blue Jackets fan or simply like to see long streaks, don't worry if Columbus is not leading after the second period. In that event, a Blue Jacket barrage on the Capitals' net seems almost certain!

UPDATE: It was not to be for the Blue Jackets, as the Washington Capitals routed them 5-0, ending Columbus's winning streak at 16 games.

*That's not to say that amazing turnarounds don't occur. Baseball's Atlanta Braves went from a 65-97 record in 1990 to 14 straight divisional titles (excluding the incomplete, strike-shortened 1994 season). Also, football's San Francisco 49ers went 2-14 and 6-10 under Bill Walsh in 1979 and 1980, respectively, before winning the Super Bowl after the 1981 season. The team would win three more Super Bowls in the decade.