Chacin in the Clutch

Opposing batters hit .212 against Jhoulys Chacin (COL) this season, but only .071 (2 for 28) with runners in scoring position.  Twenty eight at bats represents a very small sample size, but might Chacin pitch batters differently in these situations?  Is it just luck, or does Jhoulys bear down more with runs on the line?

The following are Chacin's overall numbers by pitch type:

Jhoulys Chacin 2011

Pitch type	Percent thrown	BA Allowed
Fastball	58.3%	.308
Change Up	9.2%	.067
Curveball	12.3%	.182
Slider	19.9%	.071

Batters hit his fastball pretty well, but Chacin makes up for it by fooling batters with his off-speed pitches.  When the opposition puts runners in scoring position, Jhoulys changes his pattern:

Jhoulys Chacin 2011, Runners in scoring position

Pitch type	Percent thrown	BA Allowed
Fastball	47.0%	.143
Change Up	9.1%	.000
Curveball	18.2%	.000
Slider	25.0%	.000

Chacin de-emphasizes his easiest to hit pitch, his fastball, and shows batters more curves and sliders.  He gets better results on those pitches, so it's not surprising his RISP average allowed would be lower.

The question this raises is, why doesn't he use that distribution of pitches all the time?  It might be that he wants to get batters comfortable with one approach, and then fool them with another when he really needs an out.  So far, it's working.