Nate Silver has an sharp analysis of Peter Gammons' candidates to have a breakout season in 2003. While Silver admits that "lists like these are little more than a grownup's version of pin-the-tail-on-the-donkey," he has fun giving Gammons' choices the once over using something called The PECOTA system:
As it happens, however, we're unrolling a new forecasting system at BP this year--one that is also preoccupied with the question of breakout candidates. The PECOTA system--short for Player Empirical Comparison and Optimization Test Algorithm--seeks to identify potential breakouts by comparing a player against a database of his historical peers. In so doing, it comes up with an objective estimate of the probability that a player will display marked improvement in the upcoming season (defined as an increase of at least 20% in his Equivalent Runs per plate appearance, or a decrease of at least 20% in his PERA, relative to a weighted average of his previous three years of performance).
There is a link to the complete PECOTA glossary in the article as well. Here is what Silver writes about Jeremy Giambi, whom many people feel will have a productive season for the Boston Red Sox:
I was expecting Little G to fall into the same category as Durazo: a stathead favorite who might be somewhat misplaced on this list by virtue of the likelihood of his picking up more playing time. Instead, PECOTA renders a very strong judgment against Giambi; his Breakout rate (5%) is the lowest of any player on Gammons' list, and his Collapse rate (33%) is the highest of any hitter.
The notion has been tossed around that Giambi is a breakout candidate because he's shown a growth curve similar to his older brother. Giambi the Elder does appear on his little brother's comparables list--he's Jeremy's 77th best comp, well behind such notables as Sixto Lezcano, Kevin Maas, and Mike Epstein. Sure, bloodlines might count for something, but that obscures the fact that the two Giambis aren't tremendously similar players. Jason is two or three inches taller, depending on who is doing the measuring, and he played much more regularly than his brother did early in his career, which is normally a positive developmental sign.
More importantly, though, there are important differences in their approach at the plate:
Age BB rate K rate BB rate K rate
25 12.3% 20.2% 8.5% 15.9%
26 17.0% 18.7% 9.4% 15.1%
27 19.9% 23.7% 12.3% 15.5%
Jason, while always a patient hitter, did not walk nearly as often as Jeremy did early in his career, nor did he strike out nearly as often. For a player in mid-career, Jeremy's patience borders on the absurd. He saw, on the average, 4.5 pitches per plate appearance last season; no regular player topped 4.3. About 44% of Jeremy's PAs last season ended with a strikeout or a walk, a figure that almost exactly matches Rob Deer's career average. Giambi has "old player's skills" to an extreme, and the PECOTA program thinks that players with that sort of profile don't age very well.
Why is that?
Giambi doesn't put very many balls into play, and when he does, he's one of the slowest runners in baseball. Poor speed and a high strikeout rate are both drags on batting average, and generally a combination to be avoided. Certainly, there are exceptions; some of the greatest sluggers in recent memory have put together spectacular careers with just that collection of skills.
But those hitters had substantially more power than Giambi, and provided greater disincentives for pitchers to challenge them. The worry is that Giambi's approach will cease to be effective if pitchers simply resolve to throw him more strikes. He hasn't displayed enough power, or a consistent enough ability to make contact, to suggest that he'd be able to compensate fully for a decline in his walk rate by improving his contribution in other areas.
It may not be a coincidence that Giambi's tenure in Philadelphia was the most successful period of his career to date; he was in a new league, and by virtue of Larry Bowa's infatuation with Travis Lee, his exposure to pitchers was irregular. The PECOTA system insinuates that, given repeated trials against the same set of pitchers, the weaknesses in Giambi's approach will be exploited. He'll provide the Red Sox with a multifold improvement over the most recent vintage of Tony Clark, but it's almost certain that Giambi's rate of production will be well off from last year's level.