I just performed a rather rudimentary study. According to Baseball Reference's wins above replacement, since 2001, 53% of the Twins' total WAR has come from homegrown players. 47% of their total WAR has come from players acquired outside of the organization.
During that timespan, Minnesota have averaged a 162-game record of 87-75 in which homegrown players comprise a greater amount of their total team WAR. Their average, 162-game record over a season in which players acquired outside the organization comprise the greater total team WAR is 92-70.
A couple notes:
- BBRef WAR isn't perfect, I'll admit...in fact, it's far from it. However, it is at least consistent.
- Only in 3 seasons was the team WAR particularly close between homegrown & outside acquisitions. Interpret the second note above as a grain of salt.
Total MIN WAR from homegrown players since 2001: 53%
Total MIN WAR from outside acquisitions since 2001: 47%
What conclusions can and should we draw from this matter?
Zack Greinke is about half way through the 2009 MLB season and to date he has been worth 5.5 wins. He is roughly on pace to accumulate 11 wins. As a pitcher. In the last four years, no pitcher has broken past the eight win mark. Since 2002, the first year our win values start, the highest recorded mark is Randy Johnson's 9.9 wins in 2004.... Greinke's batted balls are not significantly different from past years, but his home run rate has unsustainably dipped to just 3.3%. All in all, Greinke is missing more bats this year, but he is also throwing fewer strikes overall. Somehow he has reduced both his walks and his home runs allowed to depress his FIP to 1.98, but going forward you would expect that to be a lot closer to his 3.56 from last season. Still, with half a season banked, Greinke has a serious shot at being FanGraphs' first 10 win pitcher.
If Pettitte is a fifth starter, he is without question the best fifth starter in baseball right now, given that he would be a #3 in most other teams in the game and perhaps even a #2. Put him on some of the lesser-quality teams like the Nationals, Rockies, and Pirates and he might actually be the ace.
If the Yankees have a fifth starter, it sure isn’t Andy Pettitte, and if any of their starters is going to be relegated into bullpen duty, it should not be Andy Pettitte. People really need to start realizing that what he brings to the table is not a marginal upgrade over an average or replacement pitcher but rather almost the guarantee of +3.5 to +4 wins.