Stat Definitions

Here are some of the statistics used in The Nationals Review. Some are newfangled, some are not. But I’ll try and go over the more unfamiliar or complex ones. Also, while sites like Baseball Prospectus has dozens of different stats, I’ll try to use only a few, better for everyone’s sanity.

.###/.###/.### – This is the simple way to show the most often used and easily understood offensive stats. They are, in order, batting average/on base percentage/slugging percentage. Sometimes they are written out as such – AVG/OBP/SLG

BABIP (Batting Average on Balls in Play) – It is a measure of how many balls that are hit into the field of play, excluding HRs, end up as hits. It’s a simple calculation:

(H – HR) / (AB – K – HR + SF)

Both pitcher’s and hitters have BABIPs. For hitters, better hitters have consistantly high BABIPs, so it can be thought of as a skill. But for pitchers, with a few exceptions there is more uniformity, and can be considered a measure of luck, as well as the defense behind the pitcher. The league average for pitchers is around .300

FRAR (Fielding Runs Above Replacement) – This is the fabled VORP for fielding (see VORP below)… It’s the difference between the player’s and the replacement player’s ability to “save” runs . The average player in the league is better than the replacement player, just like VORP. It’s different for each position, but according to Baseball Prospectus, all time average FRAR for positions are as follows C-39, SS-32, 2B-29, 3B-22, CF-24, LF/RF-14, 1B-10. This means that statistically, over the course of a 162 game season, an average 3B will save 22 runs over the lowest ranking 3B, while an average 1B will only save 10 runs over the replacement level guy. This leads to the conclusion that you’d rather have a bad fielding first baseman than a bad fielding thirdbasemen fielder. This doesn’t mean a first baseman who simply cannot catch the ball wouldn’t hurt the team more, it assumes some level of competance. (FRAR2 incorporates adjustments for league difficulty and normalizes defensive statistics over time.)

IP (Innings Pitched) – I don’t like writing IP with a decimal point, so rather than writing 6.2 IP (like many do) I’ll usually go with 6 2/3.

ISO (Isolated Power) – Batting average minus slugging percentage. This stat is an attempt to show how many extra bases per AB a player generates. So for example, a .300 batting average shows that the player gets 3 hits every 10 ABs, if they are slugging .500, their ISO is .200 (.500-.300) and that ISO of .200 shows they get 2 extra bases (not 2 extra base hits, 2 extra bases, in whatever form they come) over the course of those 10 ABs.

K/BB – The ratio of strikeouts to walks, called COMMAND by Baseball Forecaster, is a strong predictor of ERA. They actually created a chart, which I am reproducing and fully quoting and giving them credit for, below:

Command Ratio Chart

Used in conjunction with K/9, it is an even stronger predictor of pitchers performance

K/9 – The ratio of strikeouts per 9 innings pitched. This is called dominance by Baseball Forecaster, and they use it to differentiate pitchers with high accuracy but little ability to strike people out and pitchers who actually strike out players. Those high K/BB, low K/9 pitchers do not perform as well as the high K/BB, high K/9 pitchers.

OPS (On-base Plus Slugging) – This is the simple addition of On-Base Percentage and Slugging Percentage. It isn’t perfect, there are stats that better reflect which hitter contributes the most, but this is easy to do, easy to understand and works pretty well.

OPS+ (On-base Plus Slugging measured against league average) – This is much more complicated than regular OPS, but it is pretty easy to interpret. OPS+ of 100 is league average. Anything above it means better than the average, anything below is worse. Think of it as a percentage, with any point above or below is that many percentage point different than league average (i.e.- an player with an OPS+ of 107 had 7 percent higher OPS than the league average, a 93 was 7 percent lower). For further explanation of this stat, and why it’s so good, check out Joe Posnanski’s website.

PA (Plate Appearances) – This is just a more accurate way of seeing a player’s trips to the plate than AB (At Bats). It is the sum of at bats, walks, hit by pitch, and sacrifice hits and flies (AB + BB + HBP + SH + SF)

Replacement Player – This is the player that is below average, one who is abundant in the minors, and is used as a basis for more complex analysis. This is set as a percentage (usually around 80%) of the average player. The stat used is runs per out, as these are the 2 most important stats. That is, a team needs more runs (not hit, walks, or homers) than the other team to win, and has a limited number of outs to accomplish this.

RC (Runs Created) – A statistic that is an attempt to estimate the number of runs a player contributes to his team. There are a multitude of formulas to determine this, and in the most basic version it is OBP x TB. This shows how much they get on base per PA and how far they go. But a more complex version includes stolen bases and that is what will be used here:

RunsCreated Formula

Even more complicated versions that include sacrifices, grounding into double plays, hits by pitch, shoe sizes, and other stats are more “technical” but the formula above is a good enough solution for the purposes of this site. It is so important because you have a limited # of outs to score more runs than your opponent, so statisticians consider runs the “currency” of baseball. Win Shares, VORP, projected team wins and things of the like are based around RC in some form or another.

QS (Quality Start) – Quite simply, it is defined as when a pitcher has at least 6IP while giving up 3 ER or less. It’s utility is debated over and over. One complaint is that someone could have lots of QS but only reach the minimum requirements (giving them a not-so-quality 4.50 ERA), but research has shown that most QS are well below this. It is preferred by sabermetricians over the Win/Loss stats because it removes much of what is beyond a pitcher’s control. Poor run support, fielding errors, and bad relief pitching can lose games where the pitcher might expect a win. However, poor fielding (not resulting in errors) are also beyond a pitcher’s control, while on the other end, allowing a high number of walks and hits is not factored in.

TAv (True Average)Baseball Prospectus measure of overall offensive contribution from a player, normalized to a league average number of .260. It is “a measure of total offensive value scaled to batting average. Adjustments are made for park and league quality”. It is set up so that if you can only look at one stat for offense to compare players, this is the best place to turn.

UZR/150 – A fielding metric that I usually look up at fangraphs. UZR stand for Ultimate Zone Rating, and it measures “The number of runs above or below average a fielder is, determined by the number of errors he makes as compared to an average fielder at that position given the same distribution of balls in play.” UZR/150 takes that number over 150 games. In other words, UZR is a counting number saying how good (or bad if it’s negative) someone is defensively. UZR/150 is normalized, so it doesn’t matter how many games they played, other than the fact that it may be a smaller sample size.

VORP (Value Over Replacement Player) – Now THIS is a complicated stat. Baseball Prospectus defines it “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.” This is over the course of a season, and obviously the more runs the better. It is calculated using league average runs and total outs created by the player, and subtracted from it is a designated replacement level player. 0 is replacement level, anything above is better, below is worse. It sounds complicated, and it is. But it is recognized as a key concept in recognizing a player’s ability by sabermetric experts. Here is a good intro to VORP by the inventor himself.

WAR/WARP (Wins Above Replacement Player) – Also known as WARP by the folks at Baseball Prospectus, WAR at Baseball-Reference and fangraphs, it is the amount of wins a player adds to a teams record over the imaginary replacement-level player. If player A has a WARP of 5 and player B has a WARP of 7, and both play the same position, if the team uses player B over the whole season, they would have 2 more wins than if they had used player A. Obviously this is conceptual, and is based on the number of runs a player adds to a teams total rather than how many times he may get up in the bottom of the 9th with 2 outs and the bases loaded. For a deeper dive, check out this post, on this site about it.

For great article on why WAR(P) is so useful, despite it’s differences, check out this great ESPN article by Sam Miller.

wOBA (Weighted On Base Average) – The fangraphs version of the overall offensive measurement. Weights batting average, on base percentage, slugging and combines them into one stat. The weights change each year, but it is set to have a similar fell to OBP in terms of whats good and bad – .400 or better is great, anything over .340 is good, below .320 is getting bad, under .300 is really bad.

wRC+ (Weighted Runs Created) – Another fangraphs offensive measurement, this one (along with plain ol’ wRC without the “+”), is a modified version of RC (listed above). Nothing majorly different in wRC than RC, it just uses fangraph’s best interpretation of the formula. the wRC+ turns it into a number similar to OPS+, where 100 is league average, and every digit above or below 100 is a percentage point better than league average.

WXRL – Expected wins added over a replacement level pitcher, adjusted for level of opposing hitters. It’s a stat for relievers showing how much better they are than the notorious replacement level guy. If they’re in the negative, they’ve done worse than Replacement Rick, if they’re positive, they’ve done better.

A Final Word on Statistics

As an aside, there are those who would say “these sabermetrics stats are a waste, people play the game, not numbers”. These people need to remember: nobody is saying numbers are more important than players. We are just trying to quantify what players do well, and what they don’t do well. Don’t be scared of “new” statistics, they are just attempted improvements on the old ones. Steven Goldman of a million baseball sites including Baseball Prospectus and the Pinstriped Bible put it best:

Moses did not come down from the mount with clay tablets showing how to figure batting average and ERA. The statistics were just made up, invented over time. They didn’t think it was worth tracking batter strikeouts at first, so no one bothered. Now we wouldn’t think of doing without batter strikeouts…On-Base Percentage was a relatively recent addition, as were saves. Game-Winning RBIs came and went. If there are new stats now, they don’t imply any more about numbers playing the game than the addition of RBIs did. They don’t diminish our respect for the human effort of a Albert Pujols or Derek Jeter any more than knowing how many times a season Babe Ruth struck out diminished the appreciation fans had for him in his day.

Enough unprovoked defense of the stats, let me know if there are more definitions you’d like to see!

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