Last season, when the Astros acquired Alberto Arias, I initially read of the transaction and just shrugged my shoulders because it didn't seem like a big deal. Then I pulled up his Baseball Reference minor league page, just to see what I could make of his stats. The thought process went like this:
- Age: 24 Good, someone under 30.
- 2.24 K:BB career, in the minors...for the Rookies farm system—especially Colorado Springs—pretty good.
- 6.99 K/9 career, in the minors...for the Rookies farm system—especially Colorado Springs—damn, that's good.
- Age: 24
- Hasn't been a starter since 2005: Crap.
- Age: 24
According to Fan Graphs, Arias throws a Fastball (74%), Slider (9.9%), Curveball (15.9%), and Change Up (0.2%). He's relying on his fastball an exorbitant amount, which maybe why someone decided, circa 2005, to move Arias to the bull pen. Of course, this is just his Major League data, and most of his appearances (both in 2007 and 2008) involved Arias coming from the pen.
Looking to his brilliant start on Sept 8, 2008, doesn't do much to dissuade me that Arias doesn't rely too strongly on his fastball to find real success as a starter. Of the 65 pitches that Arias through, 49 were fastballs (75.38%). Without littering the post with graph after graph of Arias' pitch/fx data from that start, I'll just through out a few observations and include this link for you to peruse at your leisure.
- Arias doesn't do a good job of hiding either his curve ball or his slider from his fastball, but does to a good job of hiding the slider and the curve ball in each other.
- He has very good release point in terms of hiding his pitches.
- After the first inning, Arias saw a distinct drop of in velocity from his fastball.
- He did avoid the meat of the plate fairly well.
- His fastball was much slower than it had been 10 days prior.
- He through more pitches in 2.2 innings than he did in the 5 innings ten days prior (69 to 55).
- Leaned less on the fastball 47 times (66.67%), but was probably due to the fact that he couldn't throw it above 90 very often.
- His slider becomes hidden in his fastball and change-up (which he through all of twice), leaving the curve ball as it's one distinct pitch with a BIG hump
- Instead of staying down and in on RHB, like he did 10 days prior, Arias was on in the middle to outer portion of the plate.
- Release point was not very tight, and the curveball becomes some what visible in it.
- After the 1st inning, he only through his fastball above ninety twice.