Seamheads: Measuring a Pitcher’s Ace Factor

From John Cappello at on March 13:

Without putting trust in a bottom-line assessment like the W-L record, evaluating the work of certain pitchers seems to require a statistical thesis just to back an argument. Just ask Bert Blyleven, who arguably needed a cult of sabermetric support to make his 2011 induction even remotely possible.

Not that there’s a shortage of alternatives for measuring pitching effectiveness. The raw counting numbers (IP, ER, H, K, BB) and their ratios (ERA, K/9, K/BB, WHIP) are a great first look (for many, it’s the last look). Sabermetrics kicks in when the raw data is massaged into a more useful context. Adjusted ERA (also known as ERA+), a standard at, takes a pitcher’s normal ERA and compensates for ballparks and league average ERA. The FIP methodology (Fielding Independent Pitching), a [Tom] Tango creation found on a pitcher’s dashboard at, defines a more authentic ERA in the spirit of Voros McCracken’s revolutionary DIPS theory which states that what happens once a ball is hit in play is largely out of the hands of the pitcher. Pitching dissection hits full throttle with the availability of batted-ball data, which gives us GB/LD/FB percentages, and pitch-by-pitch data, the roots of swing and contact rates relative to the strike zone.

These tools are excellent indicators of future performance. Their ability to put a number on a pitcher’s tendencies help generate virtual scouting reports.

But nowhere in this toolbox is there a stat that measures the bottom line performance of each outing with the finality of a report card grade…something like what the W-L record was used for.


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Originally published: March 14, 2011. Last Updated: March 14, 2011.