There are a variety of stats used on Red Reporter that you may not be familiar with. Most of this glossary is taken directly from The Hardball Times, Baseball Prospectus and Baseball Reference. Other useful statistical sites are Fan Graphs and The Baseball Cube (also had minor league stats).
AVG or BA
- Batting Average, Hits divided by At Bats.
- Batting Average on Balls in Play. This is a measure of the number of batted balls that safely fall in for a hit (not including home runs). The exact formula is (H-HR)/(AB-K-HR).
- Defense Efficiency Ratio. The percent of times a batted ball is turned into an out by the teams’ fielders, not including home runs. The formula is (BFP-H-K-BB-HBP-Errors)/(BFP-HR-K-BB-HBP). This is similar to BABIP, but from the defensive team's perspective. Please note that errors include only errors on batted balls.
- Equivalent Average. A measure of total offensive value per out, with corrections for league offensive level, home park, and team pitching. EQA considers batting as well as baserunning, but not the value of a position player's defense. The EqA adjusted for all-time also has a correction for league difficulty. The scale is deliberately set to approximate that of batting average. League average EqA is always equal to .260. EqA is derived from Raw EqA, which is (H + TB + 1.5*(BB + HBP + SB) + SH + SF) divided by (AB + BB + HBP + SH + SF + CS + SB). REqA is then normalized to account for league difficulty and scale to create EqA.
- Earned Run Average. Number of earned runs allowed divided by innings pitched multiplied by nine.
- ERA measured against the league average, and adjusted for ballpark factors. An ERA+ over 100 is better than average, less than 100 is below average.
- Fielding Independent Pitching, a measure of all those things for which a pitcher is specifically responsible. The formula is (HR*13+(BB+HBP)*3-K*2)/IP, plus a league-specific factor (usually around 3.2) to round out the number to an equivalent ERA number. FIP helps you understand how well a pitcher pitched, regardless of how well his fielders fielded. FIP was invented by Tangotiger.
- Fielding Runs Above Average.
- Fielding Runs Above Replacement. The difference between an average player and a replacement player is determined by the number of plays that position is called on to make. That makes the value at each position variable over time. In the all-time adjustments, an average catcher is set to 39 runs above replacement per 162 games, first base to 10, second to 29, third to 22, short to 33, center field to 24, left and right to 14.
- The percent of all batted balls (not just outs) that are groundballs.
G/F or GB/FB
- G/F stands for Groundball to Flyball Ratio. It is the number of groundballs divided by the number of flyballs (but not line drives) hit by the batter or allowed by the pitcher. It includes all batted balls, not just outs.
- Gross Production Average, a variation of OPS, but more accurate and easier to interpret. The exact formula is (OBP*1.8+SLG)/4, adjusted for ballpark factor. The scale of GPA is similar to BA: .200 is lousy, .265 is around average and .300 is a star.
HR/Fly or HR/F
- Home Runs as a percent of outfield flyballs. The home run totals are adjusted by the home ballpark's historic home run rates. Research has shown that about 11% to 12% of outfield flies are hit for home runs. For pitchers, significant variations from 11% are probably the result of "luck," but for hitters this stat is more indicative of a true skill (hitting the ball hard!).
ISO or IsoP
- Isolated Power, which measures the “true power” of a batter. The formula is SLG-BA.
- Isolated Discipline, which measures the "batting eye" of a batter. The formula is OBP-BA.
- Line Drive Percentage. Baseball Info Solutions tracks the trajectory of each batted ball and categorizes it as a groundball, fly ball or line drive. LD% is the percent of batted balls that are line drives. Line drives are not necessarily the hardest hit balls, but they do fall for a hit around 75% of the time.
LOB and LOB%
- LOB stands for Left On Base. It is the number of runners that are left on base at the end of an inning. LOB% is slightly different; it is the percentage of baserunners allowed that didn't score a run. LOB% is used to track pitcher's luck or effectiveness (depending on your point of view). The exact formula is (H+BB+HBP-R)/(H+BB+HBP-(1.4*HR)). You can read more about LOB% in this article.
- Marginal Value Above Replacement Player, as introduced in this article. MORP is modelled based on the actual behavior of recent free agent markets, and accounts for non-linearity in the market price of baseball talent (e.g. teams are willing to pay more for one 6-win player than two 3-win players).
- As listed in a player's PECOTA card, a player's MORP includes the major league minimum salary, estimated to be $325,000 for 2006. Further, in a player's Five-Year Forecast, we assume salary inflation of 5% per year through 2010 (EXCEPTION: a player's Peak MORP does *not* include the minimum salary or the inflation adjustment.)
- For 2006, a player's MORP is estimated as follows: 485000*WARP + 216000*(WARP^2) + 325000
- From Baseball Reference: We adjust all of a player's seasons from the park and league context of the seasons they played in into either a "neutral" setting (which is 100 park factor with 162-game season, 90% of runs earned, and 750 runs/team), or into a setting selected by the user with a particular year, league (with its runs/game and earned runs percentage) and home team (with its park factor).
- There is no change of role for a player, so playing time is essentially the same proportion as before, though things like At Bats go up as run scoring increases. This also means that Aaron Harang will only make 34 starts a season even if you put him in the 1914 AL.
OBP or OBA
- On Base Percentage, the proportion of plate appearances in which a batter reached base successfully, including hits, walks and hit by pitches. OBP is also a powerful performance metric when interpreted as the percentage of times the batter didn't make an out.
- On Base plus Slugging Percentage, a crude but quick measure of a batter’s true contribution to his team’s offense. See GPA for a better approach.
- OPS measured against the league average, and adjusted for ballpark factors. An OPS+ over 100 is better than average, less than 100 is below average.
- Pitches per Plate Appearance.
- Plate Appearances, or AB+BB+HBP+SF+SH.
- An adjustment made to account for the fact that some parks are easier to hit in than average, giving an advantage (in raw statistical terms) to hitters who play for that team. Park factors are always made relative to a league average of 1.00 (or 100).
- Baseball Prospectus' forecasting system. It forecasts the future for each player based on complicated algorithms and regressions. It's a reasonably accurate predictor of future performance.
PMR (Probalistic Model of Range)
- A fielding metric developed by Dave Pinto (of Baseball Musings) that tries to answer the question: what is the probability of a batted ball becoming an out, given the parameters of that batted ball? It is similar to UZR, except that it does not divide the field up into zones. The statistics and more explanation are available here.
PRC (Pitching Runs Created)
- A new stat, created by our own David Gassko. The notion behind Pitching Runs Created is that a run saved is worth more than a run scored, and PRC puts runs saved on the same scale as runs scored. You can directly compare PRC to a batter's Runs Created to gauge each player's relative value to his team. You can read more about Pitching Runs Created in the introductory article and the follow-up article.
- PrOPS stands for "Predicted OPS." It was developed by J.C. Bradbury amd introduced in this article. PrOPS isn't really a new stat; it's a formula for predicting what a player's OPS is likely to be in the future based on his batted balls, strikeouts, home runs and walks.
- A formula for converting a team’s Run Differential into a projected Won/Loss record. The formula is RS^2/(RS^2+RA^2). Teams’ actual won/loss records tend to mirror their Pythagorean records, and variances can usually be attributed to luck.
- You can improve the accuracy of the Pythagorean formula by using a different exponent (the 2 in the formula). In particular, a sabermetrician named US Patriot discovered that the best exponent can be calculated this way: (RS/G+RA/G)^.285, where RS/G is Runs Scored per game and RA/G is Runs Allowed per game. This is called the PythagoPat formula.
- Runs Created. Invented by Bill James, RC is a very good measure of the number of runs a batter truly contributed to his team’s offense. The basic formula for RC is OBP*TB, but it has evolved into over fourteen different versions. We use the most complicated version, which includes the impact of hitting well with runners in scoring position, and is adjusted for ballpark impact. RC/G refers to Runs Created Per Game, which Runs Created divided by the number of outs made by the batter, times 27.
- Runs Created Above Average. A stat invented and tracked by Lee Sinins, the author of the Sabermetric Baseball Encyclopedia. Lee calculates each player’s Runs Created, and then compares it to the league average, given that player’s number of plate appearances. Lee uses a different version of RC than we do, though the two are very similar.
- How a batter performs with Runners in Scoring Position (second and/or third base).
- Runs Saved Above Average. This stat, which is also tracked and reported by Lee Sinins, is a measure of a pitcher’s effectiveness and contribution. The formula is RA/IP minus league-average RA/IP, times total innings pitched.
- Runs Scored minus Runs Allowed.
SLG and SLGA
- Slugging Percentage. Total Bases divided by At Bats. SLGA stands for Slugging Percentage Against. It represents SLG from the pitcher's perspective.
- Total Bases, calculated as 1B+2B*2+3B*3+HR*4.
UZR (Ultimate Zone Rating)
- A fielding metric that was created by Mitchell Litchman. A partial description of the metric can be found here.
- Value Over Replacement Player. The number of runs contributed beyond what a replacement-level player at the same position would contribute if given the same percentage of team plate appearances. VORP scores do not consider the quality of a player's defense.
- Wins Above Replacement Player, level 1. The number of wins this player contributed, above what a replacement level hitter, fielder, and pitcher would have done, with adjustments only for within the season. It should be noted that a team which is at replacement level in all three of batting, pitching, and fielding will be an extraordinarily bad team, on the order of 20-25 wins in a 162-game season.
- Walks and Hits Per Inning Pitched, a variant of OBP for pitchers. This is a popular stat in rotisserie baseball circles.
- Win Probability Added. A system in which each player is given credit toward helping his team win, based on play-by-play data and the impact each specific play has on the team's probability of winning. You can read more about WPA in The One About Win Probability.
- Invented by Bill James. Win Shares is a very complicated statistic that takes all the contributions a player makes toward his team’s wins and distills them into a single number that represents the number of wins contributed to the team, times three. We have tweaked James’ original formula somewhat.
- Win Shares Above Bench, or Baseline. WSAB is a refined approach to Win Shares, in which each player's total Win Shares are compared to the Win Shares an average bench player would have received, given that player's time at bat, on the mound or in the field.
- This is an important adjustment to Win Shares, as we discovered during the 2003-2004 offseason. The bench player approach is explained in this article. It is essentially 75% of Expected Win Shares for all players except Starting Pitchers, for whom it is 60% of Expected Win Shares.
- Expected Fielding Independent Pitching. This is an experimental stat that adjusts FIP and "normalizes" the home run component. Research has shown that home runs allowed are pretty much a function of flyballs allowed and home park, so xFIP is based on the average number of home runs allowed per outfield fly. Theoretically, this should be a better predicter of a pitcher's future ERA.
ZR (Zone Rating)
- From Baseball Think Factory:
Basically, ZR is the percentage of balls fielded by a player in his typical defensive ‘zone’, as measured by STATS reporters.
The first part of understanding Zone Rating is understanding how the field is divided up.
The field is divided into 22 equal ‘slices’. Each slice runs from home plate to the outfield fence. The first slice running along the left field line is Zone ‘C’. (Zones A, B, Y and Z are in foul territory). The last zone is Zone ‘X’. Like any ‘pie’ slice, or wedge, gets wider as you approach the outfield wall. Zone C is about 7 feet wide at the third base bag, and about 20 feet wide at 300 feet from home plate.
The next 21 zones (D - X) divide the field equally until you get to the right field line. The dividing line between zones M and N runs right over second base, splitting the field in half.
STATS ZR zone grid
With this division of the field understood, ZR becomes much easier to visualize.
For infielders, only ground balls are considered for zone rating. Line drives, pop-ups and fly balls are not included. This serves to, oh so slightly, under-rate the defensive value of all infielders, but presently this information is not readily available. First basemen are responsible for all bunts that travel more than 40 feet and land in his area of responsibility.