Monday, August 29, 2011

Measuring the defense

The Twins have had far too much of this in 2011.
Monday's print column deals with the question of who should play center field for the Twins in 2012, Ben Revere or Denard Span, and in the process of writing that I gathered up this information on the Twins overall defense that won't fit.

Using the two sophisticated defensive metrics available from Baseball Info Systems on my iPad app, the Twins entered the weekend:

  • Two runs below average at first base (-2 total); 
  • Minus 8 at second base (-10 total); 
  • Minus 22 at third base (-32 total); 
  • Minus 15 at shortstop (-47); 
  • Plus four in left field (-43); 
  • Plus 17 in center (-26); 
  • Minus 5 in right (-31) 
  • Dead even at catcher (-31); 
  • Plus 10 at pitcher (-21 total)

In plus-minus, which measures plays made or not made compared to MLB average:

  • Zero difference at first base;
  • Minus 11 at second (-11);
  • Minus 25 at third (-36)
  • Minus 18 at short (-54)
  • Plus three in left (-51)
  • Plus 34 in center (-17)
  • Minus 19 in right (-36)
  • Zero at catcher (-36)
  • Plus five at pitcher (-31)


1) The Twins entered the weekend having allowed 77 more runs than the average American League team. The BIS numbers suggest the defense is to blame for 21 of those runs. I’m inclined to believe that they understate the defensive problems.

2) There are voices on the Internet complaining that Ron Gardenhire is overly critical of Danny Valencia. These numbers suggest that Valencia's defense deserves heavy criticism.

3) BIS itself is wary of putting a lot of weight on a player's single-year numbers, and playing time at every position other than third base is badly fractured, meaning that sample size make individual conclusions even more suspect. 

But with that caveat, I'll note that Alexi Casilla and Matt Tolbert accounted for 517 innings at shortstop, while Trevor Plouffe and Tsuyoshi Nishioka combined for 637. Casilla and Tolbert (as shortstops) combined are -3 in plus-minus, zero in runs saved — in other words, almost exactly average defense. Plouffe and Nishioka are a combined -15 and -15. Similarly, the second base hole is almost entirely Plouffe (-8 and -7 in just 86 innings).

4) The obvious problem areas defensively: Third base, shortstop, right field, second base.

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