As part of a fanpost that I wrote for Royals Review (that no one read, apparently), I crunched some numbers about regression for defense and bullpens that had very good showings in the previous year. The results were surprising (and depressing) on both fronts. I'm moving this here just to make sure it's put somewhere I have easy access to. The post went like this:
Bullpens do not post 7 WAR seasons 3 years in a row[*]. Defenses vary year to year[**].
[*] That's a statistically factual statement, not an assertion. Since 1990, no team has posted even consecutive
+7 WAR seasons from a bullpen. Except the Royals of the last two years.
We could all smell a little stink coming off Crow and Collins towards
the end of the season, and Yost sensed it too given their usage down the
stretch. So the health of our pen will depend on keeping new blood
flowing though the system. Donnie Joseph. Louis Coleman. Please step
forward. John Rauch, Guillermo Mota, and Brad Penny: Do not pass Go.
[**] Since DRS was created, 29 out of 30 teams that posted a +50 DRS regressed the next year. And I mean regressed A LOT. The average
regression was -58 runs. Perhaps this implies that DRS is garbage that
doesn't reflect the reality on the diamond. And to reinforce that
notion, the 2013 Royals and their +93 DRS registered as totally average
in defensive efficiency rating, as per Baseball Prospectus, turning 71%
of balls in play into outs. I loved reading about how great our defense
was last year, but I'm hoping that it was actually overrated.
