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Why The Red Sox Might Be Even Better Than They Seem

On opening day in 2016, the Texas Rangers defeated the Seattle Mariners 3-2 despite recording only a single hit, a fifth-inning single by Prince Fielder. That win helped set the tone for a charmed Texas season — it became the first of 36 one-run victories in the team’s league-leading total. The magic continued throughout the summer: Whenever they were in trouble, the Rangers seemed to have an uncanny ability to rustle up a hit.

But was it really ability? As measured by cluster luck, a statistic that quantifies the degree to which teams have either been helped or harmed by the order in which they got their hits, the Texas Rangers have indeed had the luckiest offense among playoff teams this year. And as the division series begin Thursday, a deeper understanding of the degree to which luck has affected teams’ regular-season results can help inform our expectations for them in October.

First, a little bit more on cluster luck. The idea is fairly intuitive: Some hits matter more than others because of when they occur — specifically because they come bunched together with other hits. Nine singles that are spread out over nine innings — one per inning — without any other base runners will result in zero runs. But those same nine singles would generate at least six runs if they came back-to-back in the same inning. Because we’re pretty darned sure1 that a team can’t adjust its ability to string together hits and walks,2 knowing something about how favorably those successful at-bats have been sequenced during the season can tell us whether that team might be due for a correction in the postseason.

To be fair, regression to the cluster-luck mean is hardly a guarantee. In a five- or seven-game series, so much of any given outcome is driven by random variation that something as comparatively minor as a reversal of sequencing fortune probably won’t be the driving force behind a series win or loss. But it could matter on the margins. With that in mind, this year’s remaining playoff teams are below, ranked by the total runs they’ve derived from cluster luck this season. Positive values mean more luck, and offensive and defensive elements correspond, respectively, to how lucky a team’s offensive sequencing has been — and how unlucky their opponents’ has been.

Texas Rangers +14.5 +12.1 +26.6
Washington Nationals +6.1 +8.2 +14.2
Cleveland Indians +5.3 +6.0 +11.3
San Francisco Giants -20.2 +16.8 -3.4
Chicago Cubs +6.4 -13.7 -7.2
Toronto Blue Jays -17.0 +1.7 -15.3
Los Angeles Dodgers +4.8 -23.4 -18.6
Boston Red Sox -8.1 -19.2 -27.3
Which 2016 playoff teams had the luckiest regular-season timing?

Positive numbers mean the team was luckier, whether by scoring more runs than expected on offense or allowing fewer runs than expected on defense.

Source: The Power Rank

Those charmed Rangers lead the way, having benefited in roughly equal measure from both their own offense’s good fortune and the misfortune of their opponents. The overall effect is substantial: Given the standard exchange rate of 10 runs to a win, the 26.6 “cluster luck” runs probably tacked two to three wins onto the Rangers’ total this season.

Will this affect their chances in the playoffs? Maybe.

When you start to look at the Rangers’ offensive profile through the lens of cluster luck, areas of potential concern begin to emerge. Although they’re pretty good at hitting for power (finishing fourth among the American League’s 15 teams in slugging percentage), they rank only seventh in on-base percentage. Timing is therefore especially important for the Rangers, who are relying on big hits by their sluggers to follow the comparatively rarer moments when their lower-tier hitters are on base. When those players slump, three-run homers transform into solo homers, and the overall offense suffers. If the Rangers’ luck starts to run out in the playoffs, they may look less like a 95-win behemoth and more like just another half-decent team.3

At the other end of the spectrum are the Boston Red Sox. While the Rangers gained two to three wins through cluster luck during the regular season, the Sox have probably lost around the same number.4 The Sox’s bad luck, however, is much less evenly distributed between offense and defense than Texas’s good luck. More than two-thirds has come from good fortune for the Sox’s opponents — in other words, bad luck for Boston’s pitchers and fielders — which suggests that (among other things) the Sox bullpen’s middle-of-the-pack 75 percent rate of stranding base runners may actually be a bit lower than we’d expect going forward, all things considered. That’s a good sign for Boston: a leaky bullpen can doom a playoff squad, and cluster luck suggests that the Sox ’pen was probably better than its surface-level numbers indicated this year. Perhaps October will be the month in which its strand rate — rather than Craig Kimbrel’s fastball — finally straightens out.

In between the Rangers and Red Sox are a bunch of good teams that during the regular reason broadly fell within the normal range of luck — a little fortune here, a little misfortune there. The Toronto Blue Jays’ negative offensive cluster luck reflects their boom-and-bust offense, so it was fitting that they won a crucial game on the back of a home run recently. And it’s worth noting that the Los Angeles Dodgers’ defense and pitching lost 23 runs to bad luck, the most of any playoff team during the regular season. As they take on the Washington Nationals this week, look for signs that that luck is reversing: Maybe Yasiel Puig surprises with a tremendous catch; maybe Duke Snider returns from the dead to patrol LA’s outfield. Anything could happen. It’s the playoffs.

But even as we size up the teams according to their luckiness, let’s be clear: Cluster luck isn’t the be-all and end-all of postseason indicators. Nothing is. The only thing that has been shown to correlate meaningfully with postseason success is … regular-season success. Despite October being the crapshoot that it is, better teams are still more likely to beat worse teams than vice versa, all things being equal. Cluster luck can make things slightly less equal, at the margins. And understanding the way it has done exactly that during the regular season can inform our expectations for what we’re about to see this October. May the odds be ever in your team’s favor.

FiveThirtyEight: Will Boston be too much to handle for Cleveland?


  1. See the entry for “clutch.”

  2. And the five other ways a batter can get on base.

  3. By BaseRuns, a run estimator that models how hits and walks turn into runs when sequenced randomly, the Rangers “should have” won 82 games without luck priced in — a substantial gap.

  4. That five- or six-game spread, for what it’s worth, is more than enough to make up the difference between the Rangers’ best-in-the-AL record and that of third-place Boston.

Rian Watt is a Boston-based writer whose work has appeared at Baseball Prospectus, FanGraphs, VICE Sports and The Athletic.