How (In)consistent is Jonathan Sanchez?
If you were to ask me to describe Jonathan Sanchez in one word, it would be “erratic.” It feels as though he is the embodiment of Robert Louis Stevenson’s “Dr. Jekyll and Mr. Hyde”- remarkably brilliant in one start; absolutely horrendous in the next. Every time he steps on the mound, I ask myself, “which Sanchez am I going to see today?” It gets tiresome at times, as it is more than apparent that he has the talent and the stuff to be a top of the rotation starter- but then he’ll lose his focus, and his control goes out the window. His pitch count rises, and he’s pulled out of the game by the fifth inning. But then, there are the starts where everything clicks. Nothing can get in his way; he pounds the strike zone and paints the corners with his low-90′s fastball and a slider that can be untouchable. But is Sanchez really as inconsistent as I (and many fans) think he is?
One method to check- or at the very least, estimate- Sanchez’s consistency is by looking at his Game Scores. Game Score, which is a metric developed by Bill James to evaluate a pitcher’s start, is a rather simple rating system:
1. Start with 50 points.
2. Add one point for every out recorded (3 points for every inning pitched).
3. Add two points for every inning completed after the fourth.
4. Add one point for each strikeout.
5. Subtract two points for every hit allowed.
6. Subtract four points for each earned run allowed.
7. Subtract two points for each unearned run allowed.
8. Subtract one point for each walk.
To get an idea of how Sanchez typically performs compared to the other Giants’ starting pitchers, here are the average Game Scores for each pitcher over the past two and a half seasons:
Lincecum, of course, has been full of outstanding starts over the past couple of years, although he’s scuffled a bit so far this season. Zito’s seen a nice increase in the quality of his starts, and so has Sanchez. Matt Cain has been quite good the past couple of seasons, but you already know that. What becomes very apparent is that it looks as though the Giants’ starting staff has, by and large, had well above average starts the past two seasons. No wonder they’re widely regarded as being one of the best rotations in baseball.
Now, how about that consistency? One method I like is one outlined by Rob Castellano over at Amazin’ Avenue, who uses the standard deviation of a pitcher’s game scores to get an idea of how consistent a starter is. The lower, the better. According to Castellano, the league average standard deviation is right around 16. Anything above that indicates that the pitcher is less consistent than your average starting pitcher; anything below indicates that they’re more consistent than the league average.
In 2008, both Zito and Sanchez were wildly inconsistent, in addition to having mostly below average starts. Cain was right around the average, and Lincecum was remarkably stable. 2009 saw a pretty equal distribution of consistency, as all pitchers- aside from Cain, who was very consistent- were average. And so far in 2010, we see Cain being remarkably inconsistent, with Lincecum and Zito at average, and…Jonathan Sanchez the most consistent starter? What?
That’s right- Jonathan Sanchez has actually been the most consistent starter in the Giants’ rotation in 2010. Now, let’s not confuse this for quality- remember, Lincecum and Cain have the highest game scores and are, by all accounts, the best pitchers on the staff. All this means is that Sanchez has been the most consistent at pitching around his average game score.