Mains: Rangers’ one-run record: is it all a matter of luck?

From SABR member Rob Mains at Baseball Prospectus on September 19, 2016:

The Texas Rangers have had a good season. They have the best record in the American League and have pretty much nailed down the Western Division title. But as BP alum Rob Arthur pointed out recently at, they have an absurdly/unsustainably good record in one-run games, 34-10 through September 16, suggesting that they’ve been fortunate to accumulate their total of 88 wins through that date. Our third-order winning percentage, which calculates team wins and losses using projected runs scored and allowed, adjusted for opponent quality, agrees. It pegs the Rangers as a sub-.500 team, trailing the Mariners and Astros in their division, out of the postseason.

Rangers fans would counter that the team’s one-run-game record is legitimate, as it’s the product of a good bullpen (quantifiable though questionable, as the Rangers have the worst reliever ERA in the league and have allowed the second-worst OPS+) and heart/guts/confidence/whatever (unquantifiable). How lucky, in fact, are records in one-run games?

To answer this question (admittedly, it’s been answered before) I looked at every team season since the advent of divisional play in 1969. I paired each team’s record in one-run games in a given season with its record in the following season. For example, I compared the White Sox’s 24-36 record in one-run games in 2013 with their 28-24 in 2014, and their 2014 28-24 with their 2015 29-30, etc. If performance in one-run games is a skill, there should be a correlation from one season to the next, since teams that do well one year should retain that ability in the next. On the other hand, if one-run game performance is more random, there should be very little correlation.

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Originally published: September 19, 2016. Last Updated: September 19, 2016.