More on the Phils' Luck - Run Differential

John wrote this morning about a few ways the Phillies have been lucky so far this year.  I want to add one that wasn't mentioned - based on their run differential, their win-loss total has also been filled with luck.

The Phillies run differential sits at -11.  That is fourth worst in the NL, ahead of only the Pirates, Padres, and D-Backs.  Based on this differential, they should be 13-16 rather than 15-14.

Fangraphs did a piece about run differential last week that digs deeper.  Rather than looking at actual runs scored and allowed, Fangraphs looked at expected runs.  Based on expected runs, the Phillies are even worse off.  At the time, the Phillies' actual run differential was -15, but according to Fangraphs, it should have been -28.  That's a big difference worth another one or two losses.

Baseball Prospectus has a similar running tally of the league standings.  Based on BP's method for calculating expected runs, the Phillies should be 12-17 this year, rather than 15-14.  (Though if you dig deeper and look at the strength of the Phillies' opponents so far, BP bumps the Phillies up just slightly to 13-16.)

In other words, by all measures, the Phillies have outperformed their underlying metrics so far this season.  Whether you care just about actual runs or think expected runs are better, the Phillies' record should be much worse than it is.

Here's one way to think about why this matters and how it works.  Compare the Phillies' 15 wins to the 14 losses:

15 wins: 82 runs scored versus 43 runs against.  That's a 39 run differential over 15 games.  Given that in order to win those 15 games, the Phillies would, at a minimum, need 15 more runs than their opponents, the Phillies had 24 "excess" runs in those 15 games.  That's an average of 1.6 excess runs per win.

14 losses: 36 runs scored versus 86 runs against.  That's a 50 run differential over 14 games.  Given that in order to lose those 14 games, the Phillies would, at a minimum, need 14 fewer runs than their opponents, the Phillies' opponents had 36 "excess" runs in those 14 games.  That's an average of 2.6 excess runs per Phillies loss.

In other words, the Phillies are losing games by almost a run more than they are winning them.  Basic sabermetric conventional wisdom is that very close games are more likely to be won by luck than by skill, which indicates that the Phillies have been luckier in their wins than their opponents have been in the Phillies' losses.

The one-run game totals have borne this out.  Of the Phillies' 15 wins, 7 have been by 1 run.  Of their 14 losses, only 4 have been by 1 run.

Run differential is not the final determination of a team's strength; wins and losses at the end of the year are.  But, at this point in the season, run differential can tell us that a team is likely over-performing.  Unfortunately, that seems to be the case for the Phillies so far.