Another day, another thrashing of Brad Penny, another two shutout innings at the hands of Hong-Chih Kuo. We did see a catcher's interference call, which is always a fun event because of its quasi-rarity and its quirky place in the baseball rule book.

I was chatting with MetsGeek regular and AA semi-regular Future about this last night. He was trying to figure out why the four runs Penny allowed in the fourth inning were earned, since they were all plated after Russell Martin's interference on Claudio Vargas which would have otherwise resulted in an inning-ending groundout to Jeff Kent. In fact, if you were following along with ESPN.com's play-by-play, even after the game ended, you'd have a pretty tough time figuring out what happened.

E Chavez walked.
B Schneider grounded into double play, shortstop to second to first, E Chavez out at second.
C Vargas grounded out to shortstop.
J Reyes singled to right, C Vargas to second.
L Castillo doubled to left center, C Vargas scored, J Reyes to third, J Reyes scored, L Castillo to third on throwing error by left fielder J Pierre.
D Wright homered to right, L Castillo scored.
C Beltran singled to center.
C Delgado grounded out to second.

Emphasis is mine. It's interesting that the pbp recap doesn't mention anything about the catcher's interference. Yahoo's does. At all events, the interference happened and Martin was charged with an error, his sixth of the season. So an error occurred, allowing Vargas to reach base instead of grounding out for the third out of the inning. Three hits later and the Mets have scored four runs, three of them earned.

To figure out what happened, we refer to rule 10.16(a) of the MLB Rule Book.

An earned run is a run for which a pitcher is held accountable. In determining earned runs, the official scorer shall reconstruct the inning without the errors (which exclude catcher's interference) and passed balls, giving the benefit of the doubt always to the pitcher in determining which bases would have been reached by runners had there been errorless play. For the purpose of determining earned runs, an intentional base on balls, regardless of the circumstances, shall be construed in exactly the same manner as any other base on balls.

Again, my emphasis. It turns out that despite being booked as an error, catcher's interference does not preclude subsequent runs from being charged as earned to the pitcher (though a passed ball, *not* an error, does result in runs counting as unearned). Even more bizarrely, the baserunner that reached as a result of the interference *does* count as an unearned run should he make it all the way around the bases. This little doozy is explained in the comments to rule 10.16(a).

(4) With two out, Abel reaches first on a catcher’s interference. Baker hits a home run. Charlie strikes out. Two runs have scored, but one (Baker’s) is earned, because the official scorer cannot assume that Abel would have made an out to end the inning, absent the catcher’s interference.

So Vargas's run was unearned, but Reyes's, Castillo's and Wright's were all charged to the account of Penny.