A few words on the Marlins’ run differential

After Sunday’s disappointing 4-1 loss to the Nationals, the Marlins run differential now stands at exactly -100, third worst in MLB. While it’s been a surprise to many that the Marlins have fared so poorly this season, it’s more surprising that the club managed to stay in contention through most of July with such a run differential.

In general, outscoring opponents (a positive run differential) leads to a positive winning percentage, whereas teams being outscored by opponents usually end up with negative winning percentage.  The more extreme the run differential, the higher or lower the corresponding WP%.

Yet the Marlins, now 49-60, sit only 11 games under .500, despite a run differential that suggests their record should be much worse. According to Baseball Prospectus’ Adjusted Standings,—which uses a team’s run differential—a record of 43-65 would better reflect how the Marlins have played this season. Similarly, ESPN’s Expected Win-Loss calculates the club’s record as 42-66. The large disparity between expected and actual wins makes the Marlins one of the “luckiest” teams in all of baseball, although that seems very hard to swallow. (The Cardinals, on the other hand, hold the title of unluckiest team in all of baseball.) Note: We’ll examine how the Marlins have been able to outperform their expected record in a separate post.

In what turns out to be very round numbers, the Fish’ have scored precisely 400 runs over the course of the season, while allowing 500. Only Colorado (-112) and Houston (-137) have worse run differentials, with even division rival Philadelphia only at -33. The 2011 Marlins team–whom the 2012 version were supposed to be far superior to–had a run differential of just -77 over the entire year, a mark the current club has already surpassed by the start of August.

Below are the Marlins’ run differentials shown by month, as it becomes clear where the team began to struggle:

Month  Run Differential

April        -14

May         +16

June         -63

July          -30

August      -9

Total         -100

Over the first two months, the Marlins were able to keep their differential reasonably close to 0, and were even in positive territory by end of May (+2). From that point on, however, they’ve seen a significant drop off in performance, starting with a dreadful June (-63). Since the end of May, the Marlins have posted the second worst run differential (-102) in the big leagues, again ahead only of Houston.

For a team expected to be playoff caliber, measuring the Marlins in terms of run differential yields only another reminder of this season’s disappointment. Whether reflected in the Win-Loss column or not, it will be interesting to see if the Marlins continue to be outscored by opponents, or if they can return to their early season success.

Data from Baseball Prospectus, Fangraphs, and ESPN.