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What's Gone Wrong With David Aardsma?

This is perhaps the start of a long series of posts. Or maybe not. I realize this rather implies a commitment to go through each player, but I am unsure as to how much this will interest me if the reasons end up getting repetitive. Anyways, my goal here was to take a fresh look at David Aardsma and see what has gone wrong.

Aardsma installed some hope in us of becoming a useful bullpen cog after his stellar 2009 season. I do not believe that many people fully trusted Aardsma. In fact many people noted that they expected Brandon League would eventually supplant Aardsma as the closer this season. Still, Aardsma was counted on to be another above average hard-throwing righty in a bullpen shaping up to be defined by that mold. He has not delivered on that as reliever volatility has again taught us a lesson with a swift boot to the nether regions.

Are there any underlying shifts in Aardsma's effectiveness that is driving the higher ERA, FIP, tRA, etc? To determine what has gone wrong with David Aardsma we should first point out what has not gone wrong. The first piece that I look with pitchers is information on their individual pitches. I like to note any changes in speed (might indicate an injury) or any changes in how often they throw each pitch (might indicate a changing game plan or lack of confidence). In Aardsma's case both his pitch speeds and his pitch rates are fairly stable from their 2009 figures. For all the complaining about his nothing-but-fastball approach, Aardsma has actually thrown a few more sliders this season though it still is just a paltry 9% of all pitches thrown.

If there is nothing wrong with the pitcher, are the hitters reacting differently to him? This is where I move on to where the pitches are located and how often the hitters are swinging and making contact. With Aardsma it is just more of the same however. Hitters are swinging just as often this season and though they are making contact a little more often, it is not a dramatic difference. Aardsma is throwing fewer pitches in the strike zone, but he is throwing more first pitch strikes which helps to offset that. Last season Aardsma recorded 2.35 strikeouts for each walk and hit batsmen. This season that is down to 2 flat but over just 133 batters faced, that sort of fluctuation is minimal and is driven mainly by the two hit batters compared to zero in 2009.

The final general piece to the pitching puzzle is to investigate the batted ball rates. This offers clues to pitch location or possible changes in pitch movement. When it comes to batted balls there is actually good news to be had. After developing his fly ball fetish last season, which we were all familiar with, Aardsma has upped his ground ball rate this year from 25% in 2009 to 30% in 2010.

So what's gone wrong? To the best of our current knowledge, the aspects that have actually gotten worse for Aardsma are outside of his direct control. Aardsma's strand rate (70%) has been poor for a high-strikeout reliever, but we do not have good evidence that is skill-based. The home runs have indeed regressed. While Aardsma's ERA, tRA and FIP have risen this season, it is almost solely due to those home runs, of which he has allowed all of four. Yes that is over twice the rate that he allowed last season, but last season was not sustainable. I believe that xFIP reflects the overall picture quite well. Aardsma's xFIP was 4.12 last year and is 4.18 so far this year. Aardsma has just been the victim of some bad luck.