Matthaggs expressed concern last night that Joba's transition to the rotation is not happening well.

Basically, haggs is worried that pitch count does not equal performance, that Joba's reliance upon his fastball-slider combo will not be as effective the second or third time through a lineup unless he mixes in his curve and change, too.  I think this a perfectly legitimate concern.

So my question is: How often does a pitcher need to throw his third and fourth pitches in order to keep hitters honest?  Obviously, the answer depends on how good those various pitches are. 

So far this season*, Joba has thrown his fastball 67% of the time, his slider 25%, his curve 7%, and his change only 1%.  So I set off searching for effective starting pitchers with good fastballs who mixed their pitches in a similar pattern (as there is no sortable database that I know of, this is a very unscientific, hunt-and-peck approach). I tried to select a few pitchers from (what I think of as) the categories "elite," "solid," "mediocre," and "Ponson."

Massive post after the jump...

*I'm using FanGraphs for all these pitch selection numbers; they do not include last night's game.  I'm only using 2008 numbers because the previous numbers are flawed- the Pf/x system used to assume that any pitcher could throw any pitch and identified that pitch based on movement; the current data limits the pitch options to pitches the pitcher actually throws.  It's still not perfect, but it's a big improvement.

So what trends do we see developing?

1st pitch:  Of 15 pitchers, only 3 throw their fastball less than 60% of the time, while 5 of them throw it as often as Joba has so far.  (Granted, Webb and Cain are sinkerballers, so Joba might need to dial back the fastball).

2nd pitch:  25% seems like the ideal for a second pitch.  The only guys whose second pitches are outside the 20-30% range are Ian Snell, Cain and Webb.  As noted earlier, the later two are sinkerballers, and the less Joba is like Ian Snell the happier I'll be.

3rd and 4th pitches:  This is the pitch that Joba will need to start throwing more, but not much more.  Joba has thrown 375 pitches so far this season and 26 curveballs and 4 changeups.  Throwing one extra curve or change every hundred pitches move the needle 1%, so switching one fastball to the curve/change each inning would make the third pitch jump to 14%.  20% seems like the average for third and fourth together.  Of the 10 starters with a 4th pitch, only 3 of them (Cain, Shields, and Peavy) throw more than one an inning.  

The third/fourth pitch is tricky to look at on a chart like this- is it one that the pitcher flashes to change looks on the hitter, or is one that he only uses when is second pitch is questionable?

I think Joba can be successful even if his percentages stay where they are- his great control could allow him to establish his curve and/or change early, and then he would only need to use it as a show-me.  Then again, Baseball America ranked Joba's curveball as the best in the system (since Phil Hughes' hammer was no longer eligible), so Joba could begin to go to that as often as his slider the way Sabathia and Haren mix their pitches.

Joba could learn to rely on his change more than his curve, since it breaks in the opposite direction as his slider and curve, and the 15 mph difference between fastball and change is almost unfair. 

Regardless of Joba's long term options, I see no reason to doubt that he can be effective for a couple starts throwing fastball/slider while flashing the curve and change.