Monday, September 7, 2009

TPC in Retrospect: Tommy Hanson 2009 Projection

Back in January I put together a post projecting Tommy Hanson's stats for 2009. At the time, it was hard to say how much the Braves would use Hanson, but ZiPS had him pegged for a total of 19 innings, a 5.21 ERA, and a 1-1 record. My projection wasn't perfect, but I think it was a bit better than the ZiPS projection.

To come up with my projection, I didn't simply grab some figures out of a hat. I compiled a list of comparables for Hanson and averaged out their performances during their major league season at the age of 23. At first glance, the compilation technique might not seem extremely accurate, but I think if we look a bit beyond the surface, we'll see that it is actually a very viable and mostly accurate approach.

Here's my projected line for Hanson coming into 2009:
7.9 K/9
4.1 BB/9
1.42 WHIP
4.56 ERA
.500 Win Percentage

Actual 2009 stats to date:
7.49 K/9
3.51 BB/9
1.25 WHIP
3.07 ERA
9-3 record, or .750 Win Percentage

The K/9 projection was relatively spot on, and the BB/9 projection wasn't too far off, but it would seem that my WHIP, ERA, and win percentage projections were completely obliterated. However, I would like to throw out another stat that Hanson has posted this year that will help make sense of the chaos:

Tommy Hanson 2009 tRA: 4.37

For those of you not familiar with tRA, here's the explanation given by

tRA involves assigning run and out values to all events under a pitcher’s control and coming up with an expected number of runs allowed and outs generated in a defense and park neutral environment. tRA is on a R/9 scale and does not involve any regression of the rates.

In essence, tRA gives us an idea of what a pitcher's true ERA should be given their overall performance throughout the season minus good luck and timely fielding.

Apparently, Hanson has had quite a bit of luck this season, and for whatever reason, his ERA is substantially lower than his tRA. This also helps explain why his WHIP and winning percentages seem to be so much better than my projections. Somewhere among all of his starts, there were a certain number of events that kept men off base and runners from crossing the plate while Hanson was on the mound, and his surface level stats depict a pitcher that is much different from his true production.

With that in mind, I feel like my projection of a 4.56 ERA is not far from Hanson's tRA of 4.37, and I think if we repeated the 2009 season 100 times in a vacuum, my projection would be remarkably accurate. Unfortunately, we don't live in a vacuum, and each season is only played once, and half of my projection has taken a sharp beating. I guess Tommy Hanson's good luck is by default my bad luck in this situation.

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