Bill James and Billy Beane might have started it, but an increased interest in advanced sabermetrics has led the sports world into the golden age of statistical information. Baseball isn’t the only sport either. Basketball has become increasingly “nerdy” and reliant on advanced stats. And the MIT Sloan Advanced Analytics Conference has allowed scientists, mathematicians, and sports nuts to collide.
With progress, though, comes confusion. It’s rather easy to get lost in a series of meaningless acronyms and numbers. WAR, OPS, BABIP, UZR – just what do they all mean? Shedding some light on these advanced numbers might just revise the way fans and analysts think about baseball. Here are ten important advanced stats used in baseball today.
What is it: WAR stands for Wins Above Replacement. It’s a generalized number that indicates just how good a player is versus a median major league player. In other words, if you replace an average player with a WAR of 1 with one with a WAR of 5, you in essence add four wins to your team.
How to Read WAR: WAR can be broken down into several categories ranging from 0 - 6+. A player can have a negative WAR and, in theory, a number above ten. A player with a WAR of 6 is essentially an MVP caliber player. Case in point, last year Miguel Cabrera posted a 7.2 WAR.
What is it: BABIP stands for Batting Average on Balls in Play. It represents the number of hits a player gets on balls put into the field of play.
Why is it Important: BABIP is a good indication of luck in baseball. An average MLB player will have a BABIP of .290 to .310, but if this number is higher or lower it indicates that a batter is getting ‘lucky’ when making contact. This could be a result of lucky flares and seeing-eye singles, defensive shifts, poor fielder range and so forth. Typically all hitters will regress to the mean over time. A player batting .350 with a BABIP of .400 will likely see his batting average decrease over the remainder of the season. It should be noted that over time line drives should have a higher BABIP than ground balls, and ground balls should be higher than fly balls.
What is it: UZR stands for Ultimate Zone Rating. It measures how many runs a player either saves or allows while on defense.
How it Works: Defensive statistics are tricky to quantify in general. UZR takes into account the defensive player’s arm, the amount of double plays the fielder turns, the defensive player’s range, and the number of errors he commits. Using a complex formula you end up with a UZR number than ranges from -15 to +15. Higher is better and Gold Glove quality fielders will post numbers in the low to mid-teens. Small sample sizes can greatly alter UZR, and the more a player plays the larger his UZR number might grow. The other danger of UZR is that it relies on humans to determine some of these numbers (such as errors), therefore it can be skewed by poor data. Some analysts prefer the UZR/150 statistic – which averages the UZR per 150 games.
What is it: WHIP stands for Walks plus Hits per Inning Pitched. WHIP measures how many walks and hits a pitcher gives up each inning.
Why It’s Important: A lot of pitching statistics are dependent on how well the fielder behind the pitchers play. It’s a good indication of just how effective a pitcher (and not a pitcher plus defense) is. Like a lot of pitching statistics, lower is better. A WHIP of 1 (or less than one) is excellent. While a WHIP of 1.6 is generally terrible.
What is it: DRS stands for Defensive Runs Saved. It indicates how many runs a defensive player saves when he’s on the field.
How it Works: Like UZR, DRS is determined through a complicated process. There’s seven complex fielding statistics that contribute to DRS – including, bunt runs saved (rBU), stolen base runs saved (rSB), home-run saving catches (rHR) and others. The idea behind DRS is to calculate the total runs saved, no matter the position. DRS uses the same scale as UZR (-15 to +15) and the same general estimations in ability. Also, like all defensive statistics it’s better to look at them over multiple years. Small sample sizes skew results greatly.
5 K/9 and BB/9
What are they: K/9 and BB/9 measure the number of strikeouts (K) and walks (BB) a pitcher averages per every nine innings pitched.
Why They’re Important: Like WHIP, both K/9 and BB/9 give a good indication of how many men a pitcher is walking and striking out per game. These numbers are numbers pitchers have a high degree of control over and are a good indication of who you could expect over the course of a season. Strikeout rates of 10/9 are fantastic, while 4/9 would be pretty terrible. Obviously the lower the BB/9 rate the better, but the best pitchers in baseball clock in around 1.5/9 (or lower) on average.
What is it: RF stands for Range Factor. Developed by Bill James, RF is calculated by adding the number of put-outs and assists and dividing them by the innings played. It’s supposed to give an indication of the number of outs a player participates in and how valuable they are – versus the commonly used fielding percentage number.
Why It’s Important: RF is one of the first advanced defensive stats to have been developed. It’s also flawed. Many prefer DRS and UZR to RF, though in truth it’s probably best to look at all these metrics together to get a good assessment of each player. Higher is better, and catchers and first basemen are going to always post higher RF numbers than other positions on account of the number of balls they handle.
3 Swing and Contact %
What are they: There’s a plethora of swing and contact stats for both pitchers and hitters. These look like Z-Swing% (swing percentage on pitches that are strikes), O-Swing% (swing percentage on pitches outside the strike zone), Z-Contact % (contact percentage on pitches in the strike zone), and O-Contact% (outside the zone).
Why They’re Important: Both offensive and pitching sets of swing and contact numbers give you a good indication of how much contact batters make and how often they swing at pitches inside and outside the zone. Same goes for pitchers. A pitcher who gets a lot of swings and misses on pitches outside the zone knows that pitch is deceptive and he can use that data going forward to be effective with two strikes.
2 LD%, GB%, and FB%
What Are They: These statistics measure line drive (LD), ground ball (GB), and fly ball (FB) rates a pitcher allows.
Why They’re Important: Line drives are the worst type of hits. Understanding what type of contact hitters are getting gives you a good estimate on how effective your pitcher is. Fly balls generally turn into hits less than ground balls do. Understanding what type of pitcher a team is facing can be important for defensive shifts and line-up decisions.
What is it: ISO stands for Isolated Power. It measures a hitter’s raw power and provides a good indication on how well a batter hits for extra bases.
How it Works: ISO is calculated by subtracting batting average from slugging percentage. Official statisticians use a slightly more complex formula, but the simple version works well enough. ISO needs a lot of data (at-bats) in order to generate a number which is significant and accurate. In fact, over 500 ABs is a good starting place to get a good idea of how well a batter hits for power. The better players in baseball might post an ISO of 0.250, which is excellent.