In the comments for my "eight types of pitchers" article, John noted:
Type 3 pitchers seem to be Cardinals even though they're just 4% of pitcher seasons they made up 12.5% of the Cardinals' 16man staff last season. Also, while Type 2 pitchers make up just 18% of the MLB population, they made up 31.25% of St. Louis' staff last season. They seem to be doing that by avoiding Type 0, 4 and 7 pitchers. I wonder if this could be a personal preference by pitching coach Dave Duncan. Do you have data that suggests some MLB teams look for certain types of pitchers and/or convince pitchers to use a certain percentage of their stuff?
In other words, does Cardinals pitching coach Dave Duncan encourage his pitchers to become certain types of pitchers, and not other types? Duncan has been lauded on many blogs and baseball news sites over the past couple of years due to his staffs' repeated successes. He seems to have revitalized multiple pitching careers over the past few years, including
Joel Piniero in 2009. Pitch F/X expert Dave Allen pointed out that
Duncan's pitchers get more ground balls under his tutelage than they had before.
Is there a secret to Duncan's (perceived) success in reclamation pitchers? Does he turn pitchers into specific types that are more successful, on average, than other pitcher types?
John suggests above that Duncan's pitchers tend to be type 2 and type 3, but not types 0, 4, or 7, as compared to the league average last year. For those confused about the pitcher types, please read my article
explaining the pitcher types. The types are derived from what I determine to be a pitcher's
core and
secondary pitches. All pitchers are assumed to throw the fastball as core pitch (I do not
yet distinguish between twoseam and fourseam fastballs; coming soon, Dave). As a quick reference:
 type 0: changeup core; slider secondary
 type 1: cutter core
 type 2: slider core; changeup secondary
 type 3: slider and curve core
 type 4: curve core; changeup secondary
 type 5: changeup core; curve secondary
 type 6: slider core; no secondary
 type 7: splitter core; slider secondary
It turns out that John's observation is (mostly) correct.
I looked at 20052009, rather than just 2009. I counted all pitchers for each team that threw at least 20IP. This is plenty of playing time to establish a repertoire. Here is a list of
all teams' pitcher types, by count of 20IP+ pitchers. First are the percentages, then the raw counts. I included averages and standard deviations for reference. The data is missing all pitchers who were traded midseason. Sorry.
Indeed, the Cardinals' pitchers are more likely to be type 3 (and also type 1) than an average team. The differences lie outside of one standard deviation from the norm. Likewise, the Cardinals' pitchers over one standard deviation below the norm for type 0, type 5, and type 6. The staff is within one standard deviation from the norm for type 2, type 4 and type 7.
Here is an excerpt of my full team type chart:

T_0%

T_1%

T_2%

T_3%

T_4%

T_5%

T_6%

Average
(1 STD)

719

210

1224

18

820

413

3926

Giants

10

6

17

6

11

7

41

Yankees

8

14

13

6

15

7

35

Cardinals

6

13

22

16

12

1

24

The sample size (71 pitcher seasons) is too small to conclude anything, but here are some possible explanations of what is happening:
 Dave Duncan hates changeups! Type 0 and type 5 are primarily changeup pitchers. Lots of really good pitchers have been type 5 (Greg Maddux & Tom Glavine, for example). However, very few of Duncan's pitchers fit this profile.
 Dave Duncan doesn't care for young flamethrowers (or he reforms them quickly). Type 6 pitchers are the most common type of major league pitcher, by far. Many, if not most pitchers come up to the majors as hardthrowing type 6 guys, featuring a fastball, a slider, and not much else. There is a dearth of type 6 pitchers on Duncan's staff, although the number is not ridiculously low. They still make up 24% of his staffs (league average is 33%, and the Cubs form the highwatermark at 48%).
It actually doesn't take much analysis to see that Dave Duncan's pitchers throw fewer changeups than any team in the baseball. FanGraphs has the
aggregate pitch percentages by team year. Cardinals pitchers threw fewer changeups that any other team in 2009, although they are somewhat higher in 2010 (but still solidly near the bottom).
This may just be confirmation bias, but it is entirely plausible that John is right, and Dave Duncan teaches his pitchers to throw curveballs, and not changeups. As I mentioned in my
previous piece, so far in 2010, Cardinals closer
Ryan Franklin is throwing more curveballs then even before, and would currently be classified clearly as a type 4 pitcher. Earlier in his career, Franklin used to be a slider/changeup kind of guy.
If Duncan tells his pitchers to throw curves as their offspeed offerings instead of changeups, then that would explain why his staff has an unusually high number of type 3 pitchers. I assume that conventional wisdom would dictate that a pitcher should throw a slider or a curve. Maybe Duncan is teaching his pitchers to throw both a slider and a curve. If so, that would explain Cardinals' pitchers' improved ground ball rates.
Changeups, when put in play, tend to result in fly balls (sorry I don't immediately know of a study proving it, but this makes logical sense). Thus it seems plausible that throwing fewer changeups will result in fewer fly balls. Recent advances in DIPS (defense independent pitching statistics) seems to suggest that
pitchers with high ground ball rates also give up fewer home runs per fly ball (as well as 0% home runs per ground ball).
In other words, in today's game, with short outfields walls and middle infielders who can hit one out, it may not make much sense to throw changeups for any pitcher who does not have a swingandmiss changeup.
Then again, this is just a theory. If you are interested in more data or have other ideas, drop me a line!
Looking Ahead
I trained a basic model to adjust projected FIP using a pitcher's type. For the same 20052009 span, pitchers tended to underperform my projections (ie post higher FIP), if they had types 0, 2, 5 and 6. The worstperforming type was type 5. The bestperforming type was type 1 (cutterthrowers). There were also trends from previous years' types, again suggesting that type 0 and type 5 pitchers underperform their expectations. However these are just weak trends. I will write something if/when I get something more definitive.
Strange Brew
I also ran a basic function, to figure out which teams had the most typical staffs and which had the strangest staffs, by pitcher type composition. The Cardinals have had the most unusual staff in the majors during 20052009. Closely followed by... the Brewers. So John was right in another respect. The Cardinals have the most unusual composition of pitchers in the majors during the past five years.
The most typical staff was that of the Giants, followed by the Florida Marlins.
Expect an article on this topic, as well.