One of the perennial questions surrounding players who have big seasons that are immediately credited to a change in approach is just how long those gains last. Joel Pineiro—Dave Duncan's most doctrinaire success story for the St. Louis Cardinals after a 2009 season in which he stopped striking anybody out and led baseball in walk rate—is a good case-study. He signed with the Orioles on a minor-league contract Monday, without even an invitation to major league camp.
As it turns out, Pineiro's devout Duncanism only lasted a season-and-a-half. After his big 2009 his strikeout and walk rates jumped up again in 2010, but he was still effective; in 2011 his strikeout rate fell off again, but so did his command.
The pessimistic or skeptical way to deal with that is obvious; his "new approach" lasted about a year before he fell apart again. But if you're an optimist, or you're ghost-writing Dave Duncan's memoirs, there's another way to put it: If it weren't for Dave Duncan, Joel Pineiro's 2011 season probably would have happened in 2008. After falling out of the rotation in 2007 following multiple ineffective seasons, Pineiro pushed his inevitable decline back three years by taking the words "pitch to contact" literally.
Eventually everybody's going to fall back to the baseline. Players who get new glasses or open up their swings or develop a cutter aren't immune to that, but they have bought themselves some time.