Karstens Gets that Sinking Feeling

Jeff Karstens of the Pittsburgh Pirates starts the week with the second best ERA in the National League.  His pitching improvement helped put the Pirates in contention in the NL Central.  Karstens changed his pitching philosophy in 2011.  In the past, he threw mostly fastballs:

2008-2010	wOBA	Pct
Totals	0.348	100
Fastball	0.381	46
Change Up	0.306	15
Curveball	0.249	16
Slider	0.343	15
Cutter	0.564	2
Sinker	0.402	6

Let me point out that PITCHf/x classifies that last pitch as a sinker, but given the velocity and spin, the pitch is more likely a two-seam fastball.  In 2011, Jeff features that as his main pitch:

2011	wOBA	Pct
Totals	0.290	100
Fastball	0.318	23
Change Up	0.299	12
Curveball	0.176	14
Slider	0.266	17
Cutter	0.000	0
Sinker	0.319	34

Note that the fastball and hard sinker still present batters with the best chance for offense.  Batters are no longer able to sit on the fastball; Karstens has them guessing more.  In addition, Karstens uses the pitches in different situations.  In hitters counts, Jeff goes to the fastball.  During previous seasons, he would also feature the fastball in pitchers counts, but this season, he features the sinker when he's ahead.

Karstens isn't throwing his pitches any differently.  My changing the mix, however, he's forcing batters to learn new patterns, and while that happens Jeff thrives on the mound.