Perhaps the most memorable feature of the original NBA Jam video game back in the '90s was when your player would sink three baskets in a row, light on fire, and become unstoppable. Perhaps the most memorable moments of the NBA playoffs so far this Spring have been provided by one player, the Chicago Bulls's five-foot-nine backup guard Nate Robinson, who has been unstoppable, and continues to put out against the Miami Heat. And because the world is a great place, a scientist at Yale has managed to prove why both phenomena make sense — not that actual sports teams care.
In Monday's New York Times, Gretchen Reynolds looks at sports studies headed up by Gur Yaari, a computational biologist at Yale, who looked at an entire season of free-throw shooting data in the NBA (and also 50,000 PBA bowling games) only to discover that, yes, players do really go on hot streaks over the course of a few games. Reynolds, queen of the Times most emailed list for her crossover of health and real life, explains:
In these big sets of data... success did slightly increase the chances of subsequent success — though generally over a longer time frame than the next shot. Basketball players experienced statistically significant and recognizable hot periods over an entire game or two, during which they would hit more free throws than random chance would suggest. But they would not necessarily hit one free throw immediately after the last.
For sports fans, you don't need science to prove that players step up production, in huge quantities, in short periods of time. It already happens in every sport — basketball, football, hockey, baseball, probably even bowling and volleyball, if you look hard enough at ESPN2, or play them yourself. Even casual fans pick up the chatter about someone who gets hot over four of five games, only to disappear over the next ten. To wit: Last night my cousin told me that I should pick up the Toronto Blue Jays outfielder Colby Rasmus for my fantasy baseball team after he hit a home run because "he always hits five or six homers in four or five games before disappearing again." (I do not have a fantasy baseball team.) But these studies seem to prove the hot streak is real, and historically potent; "he's on fire" is no longer the stuff of arcades and superstition — and it's early evidence that the great tradition of the streaky player (hi, Joe!) won't get cold water poured all over it once the Moneyball school of sports takes over conventional scouting and statistics.
Of course, there are statistical movements afoot that seek to downplay the role of the hot streak to a player's true value. A hot streak is unpredictable. A player makes one shot and then makes another. If things happen to keep falling, great. Give him or her the ball or puck or pass or whatever. What teams are really interested in, this line of thinking goes, is a star player's true value over the course of the season.
Major League Baseball has a number of advanced stats like WAR (wins above replacement) and VORP (value over replacement player) that seek to boil down a player's worth into an easily digestible number for executives figuring out salaries and contracts trying to get a team to the playoffs, after which point, sure, yeah, maybe that outfielder will get "hot" along with the rest of his team. The idea is that team scouts should be able to look at a single stat and decide how valuable that player is to their team, or potential team, or the team's run to a championship. Is their contribution adding value, or wins, or is there someone else we should be using?
In hockey, the stat that's becoming the most accepted is something called Corsi, a kind of advanced +/- for the Moneyball era. A player's Corsi number at the end of a game is the difference in the number of times the puck is directed toward the opposing goalie while that player is on the ice, versus the number of times the puck is directed at his team's goalie. So if your Corsi is 7+ at the end of game, you had a positive contribution to your team's offense. The Toronto Maple Leafs's Nazem Kadri defied all logistics this past regular season, though — pucks went in the net, either from Kadri or one of line mates, at an alarming rate while the rookie was on the ice. The Globe and Mail's James Mirtle explains:
...the Leafs have had a 15.3-per-cent shooting percentage whenever Kadri has played, nearly double the league average (7.91 per cent) and the highest of any forward to have played 30 games in the past six seasons.
By comparison, the average shooting percentage when Sidney Crosby, the world’s top player, has been on the ice for the Pittsburgh Penguins in those years has been closer to 12.5 per cent – roughly 20-per-cent less than Kadri.
That means Kadri is producing at the same level as the best player in hockey since Wayne Gretzky. But the common logic is that Kadri would fall back to the middle under normal circumstances. (The NHL played a lockout shortened season.) "Unless we believe Kadri is by far the best player of this era, we have to assume that in the long run he won't see as many shots go in and his point scoring rate will drop sharply — perhaps by 40 to 50 per cent," Eric Tulsky, whose TZ Quantitative Analytics boils down massive amounts of hockey data for various teams, told Mirtle.
So while studies can prove hot streaks do exist — that it's not all the stuff of superstition from us and the impossible-to-define players we believe in — teams will still ultimately rely on players who can perform over the course of an entire year, then get hot when it matters, because they're just that good. To Nate Robinson, who's been starting in place of the injured mega-star Derrick Rose, enjoy the boomshakalaka while you can, little guy.