This is the first entry in a blog associated with the publication of In Pursuit of Pennants: Baseball Operations from Deadball to Moneyball, coming out this spring and coautored by Mark Armour and me (Dan Levitt). We are crossposting this from our blog at the book's website. Thanks to the Twins Daily team for hosting.

Over the next several weeks we will be counting down the top 25 general managers in baseball history—as we see them anyway—some will signed by Mark and some by me. Because of the disparity in resources and opportunities available among the various front offices over the years, and the evolving nature of the job itself, evaluating general managers is largely a subjective exercise.

The most common approach to assess general managers objectively has largely been based on wins per payroll dollar. This is interesting and can be informative, but the goal is to win, not necessarily to win cheaply. Moreover, regardless of the money available, the challenge of building a team is highly dependent on what kind of team you start with. Brian Cashman (Yankees) and Joe Garagiola, Jr. (Diamondbacks) each had their first GM season in 1998. Cashman was handed one of history’s greatest teams, while Garagiola had a first year expansion team. Comparing their performances is not easy. How should we apportion credit (or blame) for teams that have the stamp of previous GMs? Gene Michael collected most of the players Cashman built around—how much credit should he receive for the Yankees success after he was no longer in charge?

So what did we look at in our rankings? First and foremost obviously is winning: how successful were the general manager’s teams and how consistently were they good. Constraints and resources need to be taken into account: how much freedom and authority did ownership give the GM to make decisions, build a front office, and select his on-field staff, and what were his financial restrictions? Context, too, is important. The challenge of staying on top is very different than building or rebuilding a struggling franchise. Specific direction from ownership also matters. Was the GM given a win now directive? If so, winning right away gets more weight than restocking the farm system. In other cases success over the longer term may receive more emphasis. Moreover, in some eras the competition may be unusually weak or strong, making the job either more or less challenging.

Much like with players, the very best GMs were able to oversee a team through an extended run of success, or to build a team more than once (possibly after switching teams). We give some extra credit for innovation, such as being at the forefront of a trend or being one of first to figure out how to take advantage of a structural change in the game.

Almost all GMs have records that are a mix of good and bad seasons, good and bad trades. And the trades are often judged post-facto, by how well the players performed after the trade even if those performances could not have been expected. There is a lot of luck in baseball, and we are aware that an ill-timed injury, or a key hit in a playoff series, can have a big impact on a GM’s reputation. In our rankings we have tried to strike a balance between acknowledging the impact of good fortune and giving due respect to what actually happened.

A couple of notes on eligibility. The GM role was created about 1920 — before then the players were signed or acquired either by the owner or manager. For the purposes of this exercise, we are not considering GMs who were also owners or managers of the team. If we did, John McGraw (a manager in charge of the New York Giants roster for 30 years) and Barney Dreyfuss (who owned the Pirates for 32 years and built several champions himself) would each be in the top 10. Also, note that we are ranking the men (so far, they are all men) who have run what we now call “baseball operations”, regardless of the person’s actual title. Theo Epstein is the President of Baseball Operations for the Chicago Cubs, while Jed Hoyer is the GM. For our purposes, we are crediting (or blaming) Epstein for the Cubs performance, since he is in charge.

Also, we (somewhat arbitrarily) decided to require that the candidates start their GM career by 2003, allowing for 12 years of service. John Mozeliak, Andrew Friedman, Jon Daniels and others have had impressive starts to their likely long front office careers, but we did not want to get too far ahead of their stories.

In the end this is meant to be fun. Each general manager’s challenge is unique to the time, place, environment, and ownership he reports to. We hope our career summations help illustrate aspects of how baseball’s top general managers met these challenges and provide context for their tenure.

To read more about the history of baseball operations and the GM, please buy our new book In Pursuit of Pennants: Baseball Operations from Deadball to Moneyball via the publisher or at your favorite on-line store. The top 25 GM countdown is being crossposted from our blog at the book's website.