The KC sweep and run differentials

The Kansas City Royals have completed a sweep of the Baltimore Orioles in the American League Championship Series. This follows the sweep of the Los Angeles Angels in the Division Series and the sensational one-game Wild Card playoff against the Oakland Athletics. Both the Angels and the Orioles had far superior regular-season records and significantly better run differentials during the season. The A’s had the league’s best run differential, despite their late collapse from a runaway division title to a ten-game deficit at the hands of division winner LAA. It really is hard to fathom how they are doing it. Royal blue smoke and mirrors? Best explanation I can offer.

In the just-concluded ALCS, the Royals continue to maximize wins out of few runs. In fact, their run differential is the smallest ever in a LCS sweep, by a good margin. In the series, they scored 18 runs, and the Orioles scored 12. They +6 differential beats the previous LCS record by three runs (1988 A’s over Red Sox, +9).

The +6 differential is reminiscent of the White Sox sweep of the 2005 World Series; as I noted at the time, only one prior World Series sweep had ever featured such a low differential (1950, Yankees over Phillies, also +6). Since 2005, there have been two more sweeps, but with typically large differentials (+19 in 2007 and +10 in 2012).

Obviously, the minimum possible differential in a four-game sweep is +4. So if you win with a +6, like the Royals just did, you are being exceptionally efficient in your run distribution.

Across all sweeps of best-of-seven World Series (19 of them), the average differential is +12.5. In the two leagues’ Championship Series, which have had this format since 1985 (when, incidentally, the Royals overcame a 3-1 deficit to win in seven), there have been six sweeps before this one. The average differential in those six was also +12.5. The Royals sweep was thus historic, setting a record for LCS and tying a record for all best-of-seven series. Too bad they scored that superfluous run in the top of the ninth in Game 2. They could have beaten the all-time best-of-seven sweep “efficiency” record.

(All data calculations by me, from Baseball Reference)