Sunday, August 1, 2010

Nerd Alert: FIP, Pitch f/x, & xFIP

Since the All Star Break, Stephen Strasburg had two starts and went on the Disabled List with "shoulder inflammation". Coincidentally, Josh Beckett just came off a long DL stint of his own to start two games since the break.

Beckett pitched pretty well in his two starts, both Red Sox wins: a no decision in Seattle, and a Win in Anaheim. Strasburg was his usual brilliant self in both of his performances, also on the road @Florida, and @Cincinnati.

Here are some numbers, which must be prefaced with warnings of SMALL SAMPLE SIZE. There are very neat, visual comparisons to be seen in links to Pitch f/x graphs.

Since July 15th, Stephen Strasburg got a Win in both of his starts and was just a tick off his phenomenal K/9 inning ratio, with a still sparkling: 11.12 (12.42 on the year). His ERA and WHIP were bad at 4.76 and 1.41 respectively, but much of those results look to be related to defense and luck. His Batting Average on Balls in Play (BABIP) was .438, opponents batted .305 against him, and his runners left on base percentage (LOB%) was a very unlucky 62.5%. The number that best reflects how well Strasburg actually pitched, and looks right next the graphs we'll see is his Fielding Independent Pitching (FIP), which can be measured as a sort of an expected ERA, when only looking at what only a pitcher can try to control: walks, strikeouts, and homeruns allowed. Here's the actual definition from The Hardball Times Glossary:

Fielding Independent Pitching, a measure of all those things for which a pitcher is specifically responsible. The formula is (HR*13+(BB+HBP-IBB)*3-K*2)/IP, plus a league-specific factor (usually around 3.2) to round out the number to an equivalent ERA number. FIP helps you understand how well a pitcher pitched, regardless of how well his fielders fielded. FIP was invented by Tangotiger.

Since July 15th, Strasburg's FIP was 1.17.

During the same time frame, Josh Beckett went 1-0, with a pedestrian 7.11 K/9 ip ratio. His ERA and WHIP were at All Star levels of 2.84 and 1.11, respectively. What do the luck based numbers suggest? His .280 BABIP shows he's been fortunate to have Boston's defense behind him, and the 71.4% LOB% is, I believe, pretty close to league average. He's been nowhere nearly as unlucky as Strasburg, and that's before we talk about the potential injury and the actual symptoms of pain.

Josh Beckett's FIP since July 15th: 2.48.

A 2.48 FIP sounds really good to me. Maybe we were wrong in thinking that Josh Beckett wont be worth his lucrative contract extension.

On the the Pitch f/x... I wasn't able to paste the graphs here with any data (probably protected), but here is the link for Strasburg, and this is the link for Beckett. Sorry about the technical difficulties. All the graphs I tried to post on the blog showed "No Data Found". Sorry again. When you get a chance, check out the links. They show the consistency of their release points, pitch movement, location, control, and more. It's amazing to see how consistent Strasburg has been.

Lastly, we'll finish up with the other number we like for pitching, xFIP (definition from The Hardball Times Glossary):

Expected Fielding Independent Pitching. This is an experimental stat that adjusts FIP and "normalizes" the home run component. Research has shown that home runs allowed are pretty much a function of flyballs allowed and home park, so xFIP is based on the average number of home runs allowed per outfield fly. Theoretically, this should be a better predicter of a pitcher's future ERA.

xFIP in their last two starts...

Stephen Strasburg: 2.62

Josh Beckett: 4.21

We cannot predict the future, but we can look at the data and learn from the ways history has repeated itself. People who are much smarter than me work on this stuff all the time. They are the ones blazing the trails, doing the heavy lifting, and writing the road maps that allow us to jump to conclusions and boast of the game with informed hyperbole.

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