It's no secret: The Blue Jays are in a tailspin. Injuries are piling up, they're not scoring runs and as a result the Orioles have knocked them out of first place. One more factor? They're just not as lucky.
Cluster luck is a statistical analysis that begins with this basic assumption: If a team has nine hits in a game, those hits would be spread out, one per inning. This would result in very few runs, since you're not piling runners on base to drive in. But with cluster luck, those hits are getting strung together in individual innings, which leads to more runs.
In other words: When your team is winning, everything is going their way; when they're losing, they can't seem to catch a break. When the Jays were winning, their cluster luck was high; when they started losing, their cluster luck dropped. The Jays' cluster luck peaked on June 13 at 23.58. They're now at 6.96.
The rise and fall of the Blue Jays
SOURCE: Ed Feng/The Power Rank, baseball-reference.com
What the numbers mean
Ed Feng, founder of The Power Rank, is in the business of sports analytics. One of his calculations is cluster luck. (He's not the only one, and other data analysts have slightly different formulas.)
Feng's work, originally reported on by Jonah Keri of Grantland and FiveThirtyEight, breaks down each team's offensive and defensive cluster luck, with their total cluster luck an average of the two. He uses the Base Runs formula to calculate these numbers, which compares runs scored and runs allowed against expected runs scored and allowed.
The surprising thing in the Jays' case is their offense was underperforming – or unlucky – while they were winning. On June 6, when the team reached a season high .613 winning percentage, their offense was underperforming by about five runs. As of July 9, the Jays have scored 420 runs, 19 fewer than they should have.
So why were the Jays so lucky? "Their pitchers are good at scattering hits," Mr. Feng said. By Feng's calculations, the Blue Jays should have given up 26 more runs than they have this season. The drop in the Jays' total cluster luck is a result of their bats underperforming more than they already had, and their defense not getting quite as lucky.