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This sabermetric glossary is reprinted in its entirety from the 2008 Baseball Forecaster. Note that some formulas defined here are not part of the content used on this site.

A-B | C-K | L-O | P-R | S-Z

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Abbreviations and Beginning Concepts

Ceiling: The highest professional level at which a player maintains acceptable BPIs. Also, the peak performance level that a player will likely reach, given his BPIs.

Cmd: Command ratio

Ct%: Contact rate

Ctl: Control rate

DIS%: PQS disaster rate

Dom: Dominance rate

DOM%: PQS domination rate

Eye: Batting eye

Fanalytics:  The serious, scientific approach to fantasy baseball analysis. A contraction of "fantasy" and "analytics," fanalytic gaming might be considered a mode of play that requires a more strategic and quantitative approach to player analysis and game decisions.

FB%: Fly ball per cent

FpK%: First-pitch strike percentage.

G/L/F: Ground balls, line drives, and fly balls as percentages of total balls in play (hits and outs)

GB%: Ground ball per cent

Gopheritis(also, Acute Gopheritis and Chronic Gopheritis): The dreaded malady in which a pitcher is unable to keep the ball in the ballpark. Pitchers with gopheritis have a fly ball rate of at least 40%. More severe cases have a FB% over 45%.

H%: Hit rate (batters) orHits allowed per balls in play (pitchers)

HctX: Hard-contact index

hr/9: Opposition home runs per 9 IP

hr/f: Home runs hit (batters), or allowed (pitchers), per fly ball

IP/G: Innings pitched per game appearance

k/9: Dominance rate (opposition strikeouts per 9 IP)

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Sabermetrics, Fanalytics and Advanced Concepts

Command ratio(Cmd)

(Strikeouts / Walks)

This is a measure of a pitcher's raw ability to get the ball over the plate. There is no more fundamental a skill than this, and so it is used as a leading indicator to project future rises and falls in other gauges, such as ERA. Command is one of the best gauges to use to evaluate minor league performance. BENCHMARKS: Baseball's best pitchers will have ratios in excess of 3.0. Pitchers with ratios under 1.0 — indicating that they walk more batters than they strike out — have virtually no potential for long term success. If you make no other changes in your approach to drafting a pitching staff, limiting your focus to only pitchers with a command ratio of 2.0 or better will substantially improve your odds of success. (See the Forecaster's Toolbox for more command ratio research.)

Contact rate(ct%)

((AB - K) / AB)

Measures a batter's ability to get wood on the ball and hit it into the field of play. BENCHMARKS: Those batters with the best contact skill will have levels of 90% or better. The hackers of society will have levels of 75% or less.

Control rate (bb/9), or Opposition walks per game

BB Allowed x 9 / IP

Measures how many walks a pitcher allows per game equivalent. BENCHMARK: The best pitchers will have bb/9 levels of 3.0 or less.

Dominance rate (k/9), or Opposition Strikeouts per Game

(K Allowed x 9 / IP)

Measures how many strikeouts a pitcher allows per game equivalent. BENCHMARK: The best pitchers will have k/9 levels of 5.6 or higher.

ERA variance: The variance between a pitcher's ERA and his xERA, which is a measure of over or underachievement. A positive variance indicates the potential for a pitcher's ERA to rise. A negative variance indicates the potential for ERA improvement. (See Expected ERA) BENCHMARK: Discount variances that are under 0.50. Any variance over 1.00 (one run per game) is regarded as a clear indicator of future change. 

Expected batting average (John Burnson)

xCT% * [xH1%+ xH2%]

where

xH1% = GB%*[0.0004PX + 0.062ln(SX)]

           + LD%*[0.93- 0.086ln(SX)]

           + FB%*0.12

and

xH2% = FB%*[0.0013 PX - 0.0002 SX - 0.057]

           + GB%*[0.0006 PX]

A hitter's batting average as calculated by multiplying the percentage of balls put in play (contact rate) by the chance that a ball in play falls for a hit. The likelihood that a ball in play falls for a hit is a product of the speed of the ball and distance it is hit (PX), the speed of the batter (SX), and distribution of ground balls, fly balls, and line drives. We further split it out by non-homerun hit rate (xH1%) and homerun hit rate (xH2%). BENCHMARKS: In general, xBA should approximate batting average fairly closely. Those hitters who have large variances between the two gauges are candidates for further analysis.

Expected earned run average(Gill and Reeve)

(.575 x H [per 9 IP]) + (.94 x HR [per 9 IP]) + (.28 x BB [per 9 IP])  - (.01 x K [per 9 IP]) - Normalizing Factor

"xERA represents the expected ERA of the pitcher based on a normal distribution of his statistics. It is not influenced by situation-dependent factors." xERA erases the inequity between starters' and relievers' ERA's, eliminating the effect that a pitcher's success or failure has on another pitcher's ERA.

Similar to other gauges, the accuracy of this formula changes with the level of competition from one season to the next. The normalizing factor allows us to better approximate a pitcher's actual ERA. This value is usually somewhere around 2.77 and varies by league and year.

BENCHMARKS:xERA should approximate a pitcher's ERA fairly closely. Those pitchers who have large variances between the two gauges are candidates for further analysis.

Projected xERA or projected ERA? Projected xERA is more accurate for looking ahead on a purely skills basis. Projected ERA includes situation-dependent events — bullpen support, park factors, etc. — which are reflected better by ERA. The optimal approach is to use both gauges as a range of the expectation for the coming year.

Expected earned run average2 (John Burnson) 

xER = xER%*(FB/10) + (1-xS%)*[(0.3*BIP-(FB/10))+BB]

where

xER% = 0.96 - 0.0284*G/F

xS% = (64.5 + (K/9*1.2) - (BB/9*(BB/9+1))/20 + (0.0012*GB%^2 - 0.001*GB% - 2.4) )/100

Note: xERA2 is used in the player boxes for years when G/L/F data is available. Other years use the Gill and Reeve formula.

Expected home run rate (xHR/9): See Home runs to fly ball rate

Expected Power Index (xPX)
2.6 + 269*HHLD% + 724*HHFB%

Previous research has shown that hard-hit balls are more likely to result in hits and hard-hit fly balls are more likely to end up as HRs. As such, we can use hard-hit ball data to calculate an expected skills-based power index. This metric starts with hard hit ball data, which measures a player’s fundamental skill of making solid contact, and then places it on the same scale as PX (xPX). In the above formula, HHLD% is calculated as the number
of hard hit-line drives divided by the total number of balls put in play. HHFB% is similarly calculated for fly balls.

Expected Wins (xW): (Matt Cederholm)
Intitial research, and rollout on Playerlink

First pitch strike percentage (FpK%) measures the percentage of first-pitch strikes a pitcher throws, and serves as a useful cross-check on Ctl (bb/9). Values below 60% indicate control problems, with best rates at 65% or higher. Introductory article here.

Ground ball, fly ball, line drive percentages (G/F/L): The percentage of all Balls-in-Play that are hit on the ground, in the air and as line drives. For batters, increased fly ball tendency may foretell a rise in power skills; increased line drive tendency may foretell an improvement in batting average. For a pitcher, the ability to keep the ball on the ground can contribute to his statistical output exceeding his demonstrated skill level .

BIP Type	Total%	Out
Ground ball	45%	72%
Line drive	20%	28%
Fly ball	35%	85%
TOTAL	100%	69%

* Data only includes fieldable balls and is net of home runs.

Hard Contact Index (HctX)

HCt= hard hit ball rate x contact rate
HctX= Player HCt divided by league average Hct, normalized to 100

The combination of making contact and hitting the ball hard might be the most important skills for a batter. HctX correlates very strongly with BA, and at higher BA levels often does so with high accuracy. Its success with HR was somewhat limited, probably due to GB/FB differences.

BENCHMARKS: The average major-leaguer in a given year has a HctX of 100. Elite batters have an HctX of 135 or above; weakest batters have HctX of 55 or below.

Hit rate (H%): See Batting average on balls in play 

Home runs to fly ball rate

HR / FB               

Also, expected home run rate = (FB x  0.10) x 9 / IP

The percent of fly balls that are hit for HRs. BENCHMARK: The league average level is 10%, which is also the level that individual pitching performances will regress to on a year to year basis. Batters  tend to regress to their own historical three-year mean level.