When it was announced that the A’s had won the bidding for Japanese RHP Hisashi Iwakuma, there were generally two reactions:
1. Who knew the A’s had any money?
2. Why are they spending it on a pitcher, when their starters had the lowest ERA in baseball last year?
In fact, as reports grew over the weekend that the A’s may have been the high bidder, speculation began to grow about the A’s acquiring Iwakuma in an attempt to collect depth to make a trade for a hitter. This may actually be their plan, but I’d suggest an alternative theory – the A’s starting pitching actually did need improvement.
Yes, they posted a 3.47 ERA, just ahead of St. Louis and San Francisco for the lowest among rotations in baseball last year. However, bringing back last year’s group wasn’t likely to offer the same success, as their 4.24 xFIP tied them for just the 13th-best mark in the game. The driving force behind the low ERA from their starters – a .275 BABIP (lowest in baseball) and a 74.7% LOB% (5th highest) are things that are less predictive than core performance markers such as walk rate and strikeout rate.
That doesn’t mean it was all luck, of course. Part of the A’s low BABIP (and it’s result, a lot of stranded runners) was almost certainly due to the defensive prowess of their position players. The A’s had a team UZR of +38.9, led by the best defensive infield in baseball and an outfield that often contained multiple center fielders. Their ballpark, which has the most foul territory of any in baseball, also helps keep their BABIP down. However, no matter how good your defense is, or how big your park, no team has been able to sustain an ERA three quarters of a run lower than their xFIP for any length of time. There was likely some good fortune mixed in there as well.
The ability to take advantage of the context doesn’t just belong to the pitchers Oakland already has on their roster, either. Iwakuma will benefit from the park and the defense in a similar way, but also offers the potential to be a better starter than everyone on the staff not named Brett Anderson. As a strike-throwing groundballer from Japan, the comparisons to Hiroki Kuroda are natural, and Kuroda has been one of the best pitchers in baseball since arriving in the states two years ago.
The A’s almost certainly understand that Gio Gonzalez, Dallas Braden, and Trevor Cahill were not as good as their ERAs suggest. They very well may be planning on selling high on one of those three, hoping to use their traditional numbers to acquire a position player that they wouldn’t otherwise be able to obtain. However, there’s also the possibility that the A’s recognize that they’re not going to get the same production out of their rotation in 2011 as they got a year ago, and they were simply taking a proactive step to upgrade an area of the roster that is likely to regress next year.
Dave is the Managing Editor of FanGraphs.