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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

S%: Strand rate

Save: There are six events that need to occur in order for a pitcher to post a single save...

1. The starting pitcher and middle relievers must pitch well.

2. The offense must score enough runs.

3. It must be a reasonably close game.

4. The manager must choose to put the pitcher in for a save opportunity.

5. The pitcher must pitch well and hold the lead.

6. The manager must let him finish the game.

Of these six events, only one is within the control of the relief pitcher. As such, projecting saves for a reliever has little to do with skill and a lot to do with opportunity. However, pitchers with excellent skills sets may create opportunity for themselves.

SBO: Stolen base opportunity per cent

Situation Independent: Describing a statistical gauge that measures performance apart from the context of team, ballpark, or other outside variables. Home runs, as they are unaffected by the performance of a batter's team, are often considered a situation independent stat (they are, however, affected by park dimensions). Strikeouts and Walks are better examples.

Conversely, RBI's are situation dependent because individual performance varies greatly by the performance of other batters on the team (you can't drive in runs if there is nobody on base). Similarly, pitching wins are as much a measure of the success of a pitcher as they are a measure of the success of the offense and defense performing behind that pitcher, and are therefore a poor measure of pitching performance alone.

Situation independent gauges are important for us to be able to separate a player's contribution to his team and isolate his performance so that we may judge it on its own merits.

Slg: Slugging average

Soft Stats (also, Soft Skills): Batting eyes less than 0.50. Command ratios under 2.0. Strikeout rates below 5.0. Etc.

Soft-tosser: A pitcher with a strikeout rate of 5.5 or less.

Spd:Speed score

Strikeouts per Game: See Opposition strikeouts per game.

Strike%: strike percentage

Surface Stats: Traditional statistical gauges that the mainstream uses to measure performance.Stats like batting average, wins, and ERA only touch the surface of a player's skill. Component skills analysis digs beneath the surface to reveal true skill.

Sv%: Saves conversion rate

SwK%: Swinging strike rate

SX:Speed Score Index

Vulture: A pitcher, typically a middle reliever, who accumulates an unusually high number of wins by preying on other pitchers' misfortunes. More accurately, this is a pitcher typically brought into a game after a starting pitcher has put his team behind, and then pitches well enough and long enough to allow his offense to take the lead, thereby "vulturing" a win from the starter.

Walks per Game: See Opposition walks per game.

Wasted talent: A player with a high level skill that is negated by a deficiency in another skill.For instance, basepath speed can be negated by poor on base ability. Pitchers with strong arms can be wasted because home plate is an elusive concept to them.

WHIP:Walks plus Hits divided by Innings Pitched

Wins:There are five events that need to occur in order for a pitcher to post a single win...

1. He must pitch well, allowing few runs.

2. The offense must score enough runs.

3. The defense must successfully field all batted balls.

4. The bullpen must hold the lead.

5. The manager must leave the pitcher in for 5 innings, and not remove him if the team is still behind.

Of these five events, only one is within the control of the pitcher. As such, projecting wins can be an exercise in futility.

xBA: Expected batting average

xERA:Expected ERA

xPX: Expected Power Index

xW: Expected Wins

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Sabermetrics, Fanalytics and Advanced Concepts

Saves conversion rate (Sv%)

Saves / Save Opportunities

The percentage of save opportunities that are successfully converted.BENCHMARK: We look for a minimum 80% for long-term success.

Slugging average (Slg)

(Singles + (2 x Doubles) + (3 x Triples) + (4 x HR)) / AB

A measure of the total number of bases accumulated (or the minimum number of runners' bases advanced) per at bat. It is a misnomer; it is not a true measure of a batter's slugging ability because it includes singles. Slg also assumes that each type of hit has proportionately increasing value (i.e. a double is twice as valuable as a single, etc.) which is not true. For instance, with the bases loaded, a HR always scores four runs, a triple always scores three, but a double could score two or three and a single could score one, or two, or even three.

BENCHMARKS:The top batters will have levels over .500. The bottom batters will have levels under .300.

Speed score(Bill James): A measure of the various elements that comprise a runner's speed skills. Although this formula (a variation of James' original version) may be used as a leading indicator for stolen base output, SB attempts are controlled by managerial strategy which makes Spd somewhat less valuable.

The speed scores in this book are calculated as the mean value of the following four elements...

1. Stolen base efficiency = (((SB + 3)/(SB + CS + 7)) - .4) x 20

2. Stolen base freq. = Square root of ((SB + CS)/(Singles + BB)) / .07

3. Triples rating = (3B / (AB - HR - K)) and the result assigned a value based on the following chart:

<0.001	0
0.001	1
0.0023	2
0.0039	3
0.0058	4
0.008	5
0.0105	6
0.013	7
0.0158	8
0.0189	9
.0223+	10

4. Runs scored as a percentage of times on base = (((R - HR)/(H + BB - HR)) - .1) / .04

Speed score index (SX)

(Batter's Spd / League Spd) x 100

Normalized speed scores are presented in this book to get a better read on a runner's accomplishment in context. A level of 100 equals league average speed skill. Values over 100 indicate above average skill, over 200 represent the Fleet of Feet Elite.

Stolen base opportunity per cent (SBO)

(SB + CS) / (BB + Singles)

A rough approximation of how often a base-runner attempts a stolen base. Provides a comparative measure for players on a given team and, as a team measure, the propensity of a manager to give a "green light" to his runners.

Strand rate(S%)

(H + BB - ER) / (H + BB - HR)

Measures the percentage of allowed runners a pitcher strands (earned runs only), which incorporates both individual pitcher skill and bullpen effectiveness. BENCHMARKS: The most adept at stranding runners will have S% levels over 75%. Once a pitcher's S% starts dropping down below 65%, he's going to have problems with his ERA. Those pitchers with strand rates over 80% will have artificially low ERAs, which will be prone to relapse. (See the Forecaster's Toolbox for more research.)

Strike percentage (Strike%): percentage of strikes thrown by overall pitches. Initial research here.

Swinging Strike Rate (SwK%)

An emerging indicator for predicting starting pitching performance is swinging strike rate (SwK%), which measures the
percentage of total pitches against which a batter swings and misses. SwK% can help us validate and forecast a SP’s Dominance
(K/9) rate, which in turn allows us to identify surgers and faders with greater accuracy. Introductory article here.
 

Vintage Eck territory: A pitching base performance value (BPV) level of 200 or over. Over the course of his career, Dennis Eckersely posted levels this high four times:

1989	345
1990	347
1991	226
1992	210

Walks plus hits divided by innings pitched (WHIP):Decreed as a base Rotisserie category. BENCHMARKS: Usually, a WHIP of under 1.20 is considered top level and over 1.50 is indicative of poor performance. Levels under 1.00 — allowing fewer runners than IP — represent extraordinary performance and are rarely maintained over time.

 

Walk rate(bb%)

(BB / (AB + BB))

A measure of a batter's plate patience. BENCHMARKS: The best batters will have levels over 10%. Those with poor plate patience will have levels of 5% or less.