The last two weeks have been frustrating for Yankee fans. Not only has the team lost 9 of 14 games, but six of the defeats have come in one-run ballgames. Talk about rubbing salt in the wound.
Intuitively, when games are very close, luck should play a disproportionate role. Whether it's a favorable bounce or adverse call by an umpire, the outcome of a nail biter can often be determined by factors beyond a team's control. In that sense, a club's record in one-run games is really more an indication of good fortune than good form.
Pythagorean Luck is the number of wins by which a team over performs or underperforms its run differential-based expectation.
The Baltimore Orioles and St. Louis Cardinals are two examples of teams whose performances in one-run games have tilted the balance of their seasons. The Orioles, who have been outscored by 60 runs, have trumped their Pythagorean expectation by nine games thanks in large part to a league leading winning percentage of .769 in one-run ballgames. Meanwhile, the Cardinals, who boast baseball's best run differential, have lagged in the standing because they've only been able to win 12 of 30 games decided by one run. Are both discrepancies simply a matter of luck?
Source: Baseball-reference.com and fangraphs.com
Interestingly, the Orioles' bullpen ERA of 3.22 ranks as one of the best in the game, while the Cardinals' relief ERA of 4.24 is down toward the bottom. Overall, bullpen ERA and winning percentage in one-run games have exhibited a moderate inverse correlation (R=-0.45) this season, so, if luck is playing a role, some of it may be the residue of design. However, unfortunately for the Yankees, whose relievers have been every bit as good as the Orioles (albeit in fewer innings), this relationship hasn't translated in quite the same way.
Note: Red markers indicate World Series championships; yellow markers indicate A.L. pennants.
The Yankees 13-15 record in one-run games not only ranks near the bottom of the league, but would also qualify as one of the lowest marks in franchise history, particularly among contending teams. Combined, the franchise's 40 pennant winners have posted a .563 winning percentage in one-run contests, and only four (and two World Series victors) were below .500 in an individual season. So, if you're into omens, it might be a good idea to root extra hard the next time the Yankees find themselves in a close game. The team's performance in October just might be depending on it.