Nate Silver, an author at Baseball Prospectus, is also the man behind PECOTA, one of the most innovative and accurate baseball forecasting systems around.

In addition to comparing baseball players throughout history in unique and meaningful ways, PECOTA is different in that it provides not one prediction per player, but a range of predictions along with the likelihood that each shading of that range will be the end result. As Nate explains,

While a majority of players of a certain type may progress a certain way--say, peak early--there will always be exceptions. Moreover, the comparable players may not always perform in accordance with their true level of ability. They will sometimes appear to exceed it in any given season, and other times fall short, because of the sample size problems that we described earlier.

PECOTA accounts for these sorts of factors by creating not a single forecast point, as other systems do, but rather a range of possible outcomes that the player could expect to achieve at different levels of probability. Instead of telling you that it's going to rain, we tell you that there's an 80% chance of rain, because 80% of the time that these atmospheric conditions have emerged on Tuesday, it has rained on Wednesday.

PECOTA is a truly fascinating system, and if you haven't gotten around to poking around the PECOTA "cards", you should get on the ball and at least peruse the freely available Red Sox forecasts.

Conveniently enough, Nate also authored the Cubs chapter in this year's edition of BP's annual book, Baseball Prospectus 2005. Nate was kind enough to participate in a short Q&A about a few things PECOTA and BP have to say about this year's Cubbies.

Cub Town: I think you nailed Jim Hendry's strengths and weaknesses in the essay that opens the Cubs chapter in BP 2005. He's a GM who's quickly shown he's good at getting the big things right (trading for Nomar) but doesn't always make the correct decisions with the small bits (re-signing Neifi). What are some small moves that you think could help improve the current Cubs team?

Nate Silver: Getting just one big bat coming off the bench would make the roster look an awful lot different. Particularly good would be someone like Florida's Josh Willingham, who can play a couple of different positions. I don't mind having Blanco or even Neifi around as defensive replacements--the problem is when they double as your pinch-hitters.

CT: Do you think the Cubs' front office is too influenced by Dusty Baker?

NS: I think they're too deferential to Dusty Baker. My guess is that Jim Hendry and Andy MacPhail are usually not calling Baker into their higher-level planning meetings, but they do think a lot about putting together a team that will get along with one another, and that necessarily means getting along with Dusty. Something like the trade of Choi after 2003--I don't know that the front office appreciated his value to begin with, but the fact that Dusty didn't like him might have been the decisive factor.

The irony is that I think if you had a more strong-willed general manager who was willing to put Dusty in his place at certain times, you'd have yourself one of the very best managers in the game. But I don't know that Dusty would want to work under those circumstances.

CT: PECOTA thinks Jason Dubois, while he won't hit like Moises Alou, version 2004, can hit like Alou, version 2005. There are questions about how much playing time Dubois will get, but how much sleeper potential do you think he has?

NS: I don't know that Jason Dubois is a sleeper; I think he's pretty much a known commodity. There are a few examples on his PECOTA comparables list--like Derrek Lee and Jay Buhner--of guys that continued to improve throughout their twenties, but even if he just repeated the production he gave them at Iowa last year, that would represent a substantial upgrade over Hollandsworth or Hairston. You know it's bad when even Phil Rogers is jumping on the "Free Jason Dubois" bandwagon.

CT: PECOTA isn't terribly hot on Nomar Garciaparra becoming an elite hitter again. What are the biggest factors in the good-but-not-great projection for Nomar, and do you think he's a good bet to outperform the projection?

NS: I don't think he's a particularly good bet to outperform his projection, though I do think he was a fine signing at the price they got him. Nomar has three or four strikes against him from a projection standpoint:

1. Batting average is usually the first skill to deteriorate as a player ages, so a guy who is relatively more dependent on it won't tend to age as well.
2. Nomar's secondary skills are also in decline. His isolated power has dropped for three or four years running, and he stole just four bases last year.
3. Middle infielders don't tend to age that well.
4. Injury-prone players don't tend to age well, even if they manage to remain relatively healthy.

CT: On the other hand, the player comment (and PECOTA forecast) for Corey Patterson in BP 2005 is very positive. Other projection systems, such as the work of Ron Shandler, are much less optimistic. Why do you see good things ahead for Patterson?

NS: I remember writing an article for the New York Sun last year on Corey, which involved preparing a list of players who already had pretty good power, and then substantially improved their plate discipline at some point in their early 20s. I can't seem to find that list right now, but it was full of very, very impressive names--guys like Johnny Bench and Dwight Evans and Albert Belle.

Basically, if you're going in with a lot of natural talent, and you demonstrate an ability to improve your hitting approach on top of that at a young enough age for the improvement to be sticky, there's a good chance you're going to be a star. If anything, I think that PECOTA is on the low side with Patterson.

CT: PECOTA looks through the Cubs' minor league pitchers (and the bottom of their Major League staff) and sees lots of pitchers capable of putting up seasons with mid-4.00 ERAs now. Michael Wuertz, Todd Wellemeyer, and John Leicester are no surprise, but Bobby Brownlie and Chadd Blasko also fit this profile. Are the Cubs really as deep pitching-wise as PECOTA makes them seem?

NS: I think so. The organization does a fine job of scouting and developing pitchers. The question is how you leverage all of that. We usually criticize teams who are too quick to trade their prospects, but with pitchers there are more things that can go wrong than can go right, so I wouldn't mind seeing some moves if it can help the organization elsewhere.

CT: PECOTA is even more optimistic about Angel Guzman (15.9 VORP) and Sergio Mitre (15.2 VORP). Guzman's a well-known prospect, but Mitre often flies under the radar. Do you like Mitre as much as PECOTA does, and what kind of pitcher do you think he could turn into given the right opportunity?

NS: One thing that helps Mitre's projection is that we were able to get groundball-flyball numbers for minor league pitchers this year. Mitre does an extraordinarily good job of keeping the ball down, which is absolutely essential when you don't have dominant stuff. I don't see that much difference between someone like Mitre and someone like Carl Pavano.

CT: Finally, how much do you love Carlos Zambrano?

NS: He's probably my favorite baseball player right now. Whenever I think about his pitch counts, though, I just keep hearing Ralphie's mother tell him "You'll shoot your eye out, kid!".

Cub Town thanks Nate Silver for taking the time to answer these questions.