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Hello Outlier

Posted By Dave Cameron On November 7, 2008 @ 12:00 pm In Daily Graphings | 13 Comments

Word trickled out this morning that the Houston Astros had re-signed LaTroy Hawkins to a one year deal for $3.75 million. That seamed a bit cheap to me, given what pitchers are getting in free agency these days, so I took a closer look at Hawkins’ numbers to see if I was missing something. What I found was one of the strangest outliers I’ve ever seen.

Check out Hawkins’ batted ball graph:

GB/FB/LD

Look at that ridiculous spike in GB% during 2007. His whole career, Hawkins has been an average groundball guy, but in 2007, he became the relief pitching version of Brandon Webb, just without all the strikeouts. It wasn’t a small sample size thing, either – Hawkins faced 225 batters in 2007 while pitching a full year in relief for the Rockies. Out of nowhere, with seemingly no explanation, his GB% jumped from 44% to 63% in a single year.

As you’ll notice from the graph, the trend didn’t continue in 2008, as his GB% fell back to 46.1%. He offset the lack of groundballs by returning his strikeout year to 2005 levels, posting a 6.97 K/9. His 3.28 FIP in 2008 was the best he’s posted since 2003.

So what happened? GB rates have extremely high year to year correlations, and they normalize very quickly. You just don’t see huge swings in groundball rates from year to year like this. The odds of it being random variation are extremely slim. It is much more likely that Hawkins changed his approach in some way during the ’07 season, decided he didn’t like the results, and scrapped it for 2008. However, I haven’t been able to find any evience that this is true.

So, Rockies/Astros fans, what have you got? What happened to LaTroy Hawkins in 2007, and why didn’t it carry over to 2008?


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