We all should be aware that the starting pitching has improved. That didn't take much, to be honest. But I wanted to pinpoint one stat to measure just how much improvement has happened and which of the pitchers is most responsible for it. That stat is game score, which is a fairly simple method of measuring starting pitching effectiveness. Basically, every pitcher starts with 50 points, and points are added or taken away depending on things like runs, strikeouts, innings pitched, and so forth. The average game score for the Diamondbacks this year is 44, with only the Twins (42) getting worse performances from their starters.
Bronson Arroyo's 7 shutout innings last night gave him the highest game score of any D-backs pitcher, with a 76. This was the third time in the last two trips through the rotation that a new high was reached. Prior to last night, the best game score was a tie at 69 between Mike Bolsinger and Josh Collmenter. This was the lowest highest score in the major leagues. The Diamondbacks are saved from having the lowest game score in the major leagues; despite Arroyo posting a 4 (4!) against the Mets, Felipe Paulino was able to get a -5.
This looks pretty bad. But it is a substantial improvement. According to Jeff Angus (http://sabr.org/research/does-game-score-still-work-today-s-high-offense-game) teams whose starting pitchers had a game score of 43 or less (in 2007, it would only be more true today) had a winning percentage of only .244. The Diamondbacks have had an astounding 14 such games, and managed only one win (over the Giants with Randall Delgado on the mound), for a winning percentage of only .071. However, in games where the starting pitching is simply respectable, the record is substantially better. The D-backs are 9-9 when getting simply respectable starting pitching (anything 44 or higher), which is below the averages in 2007, but is substantially better than the overall record.
Based on this, it's easy to say that the key going forward is to continue the improvements the rotation has made since leaving for Chicago. While it would be nice to get performances like Arroyo gave every time out, simply being average consistently would be a step in the right direction.