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The Astros Base Running: Why have a Green Light?

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For the season, the Astros are 17/30 in stolen bases.  That's is not a good ratio, and is definitely not a good ratio to have when your team is in the basement of the league in terms of of OBP.  It's hard to quantify the linkage between a stolen base/caught stealing in a game state to to the events of the rest of the inning, but some simple tools exist to inform us whether the cost/benefit of the stolen base makes sense anymore.  With these somewhat crude tools, I want to take a look at the effect of having a "green light" on the base paths for a lot of the Astros.

 

A stolen base (SB), according to TangoTiger, is valued at .19 of runs, purely because it moves the runner over.  This the marginal effect that a stolen base has on run expectations.  The flip side, getting caught stealing (CS) has a value of -.44, meaning that it marginally reduces the run expectation by .44. We can break the CS run value up further, by looking at how it reduces the run expectations. It has an “inning-killing effect” of -.16 and a “moving the runner over effect” of -.02. The other -.26 is the "getting on effect" because creating an out reduces the likelihood that the next batter gets on.

At face value, we can see that stealing bases is a bad proposition because the marginal benefit exceeds the marginal costs—unless you have a “sure thing,” like Michael Bourn (who's 8/10 so far this year).  

Doing so simple multiplication, we discover that so far this season, the green light policies base running.  The Astros have, roughly, added 3.23 runs with via the stolen base, but have lost 5.72 runs with CS.  That's a net result of -2.49 runs in 26 games, which isn't a ton.  However, it's actually kind of a significant impact.  In 30 stolen base attempts, they have cost themselves .08 runs per attempt.  Again, this isn't a significant sounding number, but consider the fact that Astros have averaged about 4 runs a game so far this year, as that that equates to an average of .47 runs per inning (4/8.5, accounting for the sometimes played bottom of the ninth), and the significance starts to appear.  The average value of a steal attempt for the Astros then is actually 17% of the average runs per inning, in the wrong direction.  Begging the question: Why the Green Light?

This isn't the most significant exploration of base running metrics, but it gets to the point pretty effectively.  The risk/reward, cost/benefit, whatever something/something you want to use, doesn't justify such a lose running game.

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Some of you may have noticed my rather conspicuous absence over the last few days.  On Friday I finished a week long blaze of late nights and paper writing to complete my undergraduate career and then took a few days of much needed celebration and reveling with all my friends before we go our separate ways in a week or two.  Expect me to be a little lax for the next few days while I squeeze in all the stupid stories I can, and then I'll get back to spending entirely too much time, thinking and writing about the Astros.