Introducing the Ace Barometer

According to the Ace Barometer, Roy Halladay is the best in baseball. Brad Mills/US Presswire

With last season being dubbed the "year of the pitcher," and scoring down even further this year, it's no wonder that most of our focus these days is on the men on the mound. And with Josh Beckett and Cliff Lee facing off Tuesday, and Jon Lester and Cole Hamels throwing down Thursday afternoon, it got those of us at Insider thinking about "aces."

But how is one defined? Baseball Prospectus' Kevin Goldstein attempts to get a subjective definition elsewhere on Insider today, and while there is merit to Justice Potter Stewart's "I know it when I see it" line of reasoning, why settle for the subjective when the objective is sitting write in front of us?

To that end, I've created the "Ace Barometer," which was inspired by "The Eliminator", a college football series by Insider's Jeff Dooley that attempts to predict the national champion based on certain statistical benchmarks.

In an attempt to statistically define an ace, I went to the indispensable Baseball-Reference.com Play Index. I began at the start of the 2009 season and entered the following parameters: A strikeouts-to-walk ratio of greater than 3.0, fewer than one home run allowed per nine innings and an adjusted ERA of at least 125, which is 25 percent better than the league average.

Why those numbers? For starters, I wanted to have a decent enough sample (2½ years in this case) to weed out any one-year wonders. To truly be an ace, you have to maintain a high level for a few years in a row. The Rays' James Shields has been a beast this year but has been inconsistent throughout his career, and I don't think we can call him an ace.

As for strikeouts, they had to be included because they are the best indicator of dominance. But strikeout rate alone doesn't do the trick. If it did, the Giants' Jonathan Sanchez would be considered an ace, and aces have to control the strike zone. However, if you're whiffing three times as many men as you walk, you're doing a heck of a job -- just 24 qualified starters pulled it off last year.

Now, it's not imperative to be stingy with home runs because they don't hurt you too much if you're not putting a lot of men on base. That said, it's tough to be an ace if you're gopher ball-prone, and the easiest way to avoid big innings is to keep the ball in the park.

I added ERA+ in order to adjust for league and ballpark. Because let's face it, some leagues and parks are a lot tougher than others.

After entering the above criteria, these are the nine names that were spit out (arranged in descending order of ERA+, minimum of 40 starts since Opening Day 2009):