FOXSports Sabermetrics Glossary

There are many advanced baseball statistics that can help you forecast player performance; below are a dozen that will help you start down the road to fantasy glory. We could probably write entire articles on each of them, but consider this an introduction. And remember: No number represents an absolute guarantee of anything.

BABIP (Batting Average on Balls in Play)

For hitters: An at bat can result in a home run, a strikeout, or a ball “in play.” In 2013, the average BABIP for hitters was .297, and it’s usually somewhere around .300. Why do we care? Because extreme BABIPs – like .250 or .350 – are often indicators of bad luck and good luck, respectively. Over a short period, or even a season, a very strong BABIP suggests that a batter is experiencing some good fortune in “hitting ‘em where they ain’t,” and a weak BABIP the opposite. This luck factor will mainly affect batting average, but runs scored, RBI and stolen bases are impacted as well.

Let’s take Cubs 1B Anthony Rizzo. His BABIP in 2013 was .258, which was the ninth-worst mark in the majors, and a big factor in his .233 batting average. If Rizzo had a track record of bad BABIPs, we could attribute it to something like an inability to make good contact. However, Rizzo’s minor-league BABIPs were pretty good, and his mark with the Cubs in 2012 was .310. While there are no guarantees that Rizzo’s 2013 BABIP will improve, it probably will. Keep that in mind when your competitors are spooked on draft day by his bad batting average.

Can other factors affect a hitter’s BABIP? Sure. A ballpark with a large outfield – Coors Field, for example – will see more hits drop in. Fast runners that get many infield hits (like Mike Trout) and batters with high line-drive rates (like Joey Votto) tend to have above-average BABIPs, and the converse is true for slow guys who hit the ball in the air a lot. But for most players, we should assume a BABIP close to .300.

For pitchers: BABIP is even more important here, because the pitcher has less control over what will happen when the ball is hit. That’s why high-strikeout pitchers are more reliable – a strikeout isn’t subject to a weak fly ball falling in front of an outfielder, or getting past a slow shortstop.

You might be thinking, “This is stupid, because great pitchers induce weak contact.” This may be true … to a point. Some aces (like Clayton Kershaw) have consistently low BABIPs. However, the MLB average for pitcher BABIP in 2013 was .294, and Justin Verlander’s was .316. Sometimes, you just have bad luck.

Again, while we can’t predict BABIP, we can assume that most guys will have a number that settles near the league average, and/or near their career averages (which should also be looked at). Good or bad defense can have an effect, as can letting batters rip line drives everywhere (like Ricky Nolasco). Otherwise, we can look at a guy like Verlander – who carries a .288 career BABIP mark – and reasonably figure that his 3.46 ERA will drop. There were probably other factors in Verlander’s subpar season, but bad luck didn’t help.

For both: For a number of reasons, there are hitters and pitchers with BABIPs that consistently defy the league averages. Your focus should be on the outliers – BABIPs that stick out like a sore thumb in someone’s stat line. Michael Cuddyer’s career BABIP is a pretty normal .310, so why was it .382 last season? Luck, most likely.

LOB% (Percentage of Runners Left on Base)

For pitchers: This is the percentage of runners a pitcher strands on base over the course of a season. LOB averages are usually in the low 70s, and last year’s MLB average was 73.5%. While your ace-level, high-strikeout guys will tend to have higher-than-average LOB rates – because they retire more batters whether or not runners are on base – most pitchers will regress toward league average.

Example: Seattle’s Hisashi Iwakuma was second in MLB with an 81.9 LOB% in 2013, and had the same rate in 2012. Is it possible that Iwakuma has an innate ability to pitch amazingly well with runners on base? Sure, but it’s not likely. Iwakuma is a pretty good pitcher, but don’t look for a 2.66 ERA again.

GB% (Percentage of Ground Balls to Balls in Play)

For pitchers: The average MLB ground-ball rate in 2013 was 44.5 percent. Even though ground-ballers can be punished by bad fielders, generally a strikeout/ground-ball combo is good, because it keeps balls from going over fences. Even a ball in play is better than a home run from a pitcher’s perspective, right?

The top five ground ballers in 2013 were Justin Masterson (58% GB, 3.45 ERA), A.J. Burnett (56.5% GB, 3.30 ERA), Rick Porcello (55.3% GB, 4.32 ERA), Doug Fister (54.3% GB, 3.67 ERA) and Jeff Locke (53.2% GB, 3.52 ERA), and most of their ERAs were solid. Burnett, in particular, is a good example of how posting above average numbers in both K% and GB% can lead to success. Felix Hernandez and Stephen Strasburg are better starters who were very good in both categories. Ground balls by themselves are not a good indicator of performance, but by inherently allowing fewer homers, pitchers who keep the ball on the ground have a head start over their fly-balling counterparts.

HR/FB% (Fly Ball to Home Run Ratio)

For pitchers: This is the numbers of home runs given up per every fly ball allowed. Pitchers with home games in small ballparks will tend to have higher HR/FB ratios, with the opposite in larger parks, but generally the average is close to 10 percent (last year’s was 10.5). If you see an extreme HR/FB rate – like Anibal Sanchez’s 5.8 from last season – you should remember that it’s more likely to regress toward the league average than to stay where it is.

For hitters: Batters have more control over HR/FB ratios, because some guys just hit the ball farther than others – like Chris Davis, who had a 29.6% HR/FB last season, and 25.2 in 2012. Also, slappy guys who hit singles all the time will tend to have lower HR/FB rates. This is a better stat for judging pitchers than hitters.

However, outliers still exist here. Hey, Will Venable – why did you post a 19.8 HR/FB rate in 2013 (ninth-best in MLB) after maxing out at 11.2 percent in your three previous seasons as a regular? Maybe you got stronger, but maybe you got a little lucky. We’re not expecting 22-plus homers again, fella.

K/BB (Strikeout to Walk Ratio)

For pitchers: Unless you want to trust a more encompassing stat like FIP or xFIP (which we encourage), K/BB is a nice, easy rule of thumb you can use to predict a pitcher’s effectiveness. Thanks to our strikeout-happy era, last year’s ratio of 2.51 strikeouts to every walk was the highest of all time.

While K/BB is helpful, if the strikeout rate isn’t high enough – maybe 7.5 whiffs per nine innings or better – a pitcher will be subject to the previously mentioned luck factors. Still, none of 2013’s top 20 K/BB pitchers had ERAs above 3.95, and only five of them were higher than 3.50. That’s pretty good, and speaks to the general effectiveness of a pitcher who strikes people out and limits free passes. Some people think K/BB should be tweaked a little – but as is, it helps.

Strikeout per nine innings (K/9) and Strikeout Rate (K%)

Though used for both pitchers and batters, this stat is more indicative of a pitchers’ performance, measuring how many strikeouts are averaged over nine innings. As a punch-out is one of the few outcomes pitchers can control, the higher the rate, the better, and improvement in this category likely correlates to an enhanced ERA and WHIP. (For example, part of R.A. Dickey’s 2012 success can be attributed to his jump from a 5.78 K/9 in 2011 to an 8.86 mark in 2012.)

The league mean is around seven strikeouts per nine innings, with an average above eight considered solid and below six deemed poor. Yu Darvish led all starters last season with an 11.89 K/9 rate.

In reference to batters, a strikeout rate is the more envied approach, as it accounts for plate appearances. A high strikeout rate is not always a red flag, as power hitters tend to have inflated figures, yet an enlarged strikeout percentage versus past production is a signal of hitter regression. The league average is around 19 percent, with a number under 13 percent considered good and over 21 percent deemed bad. Chris Carter led the majors with a 36.2 strikeout percentage last season, while Norichika Aoki had a league-low 5.9 percentage.

Isolated power (ISO)

To obtain isolated power, subtract a player’s batting average from slugging percentage. This number illustrates a player’s extra-base hits and offers a window into a player’s strength and power.

ISO is better used as a forecast tool, in the sense of what to expect from extra-base production. Though it can be utilized to show what a rising star is capable of, it’s better application is to denote when a slugger is heading for regression.

League average hovers around .148, with a mark above .200 deemed solid and below .110 substandard. Chris Davis led the majors in 2013 with a .348 ISO.

Line Drive percentage (LD%)

Simply, how many batted balls are deemed line drives? According to, a line drive produces 1.26 runs per out, compared to 0.13 runs from fly balls and 0.05 runs for grounders. Basically, hitters are striving for liners while pitchers try to avoid them.

The league mean for line-drive percentage is around .20, meaning pitchers that are under this figure are usually successful, whereas a higher concession of liners translates to failure. (For hitters, the opposite is true.)

If a pitcher unexpectedly struggles, a look at his line-drive percentage can give a sense of the issues. For batters, a high line-drive percentage should signal a robust batting average, as the trajectory of these shots, compared to grounders and fly balls, are the most likely to be hits.

Fielding Independent Pitching (FIP)

Measures three outcomes that pitchers are responsible for – walks, home runs and strikeouts as, to some degree, every other result is a product of chance. A homer does the most damage, while a walk has more impact than a strikeout. FIP highlights a pitcher’s performance apart from his team’s defense and computes to a number similarly digested as ERA. This number illustrates how well a pitcher should have performed over a given period of time.

Major discrepancy between a pitcher’s FIP and ERA can assist as an indicator for future progression or regression, as a FIP higher than ERA signals luck was involved, whereas a lower FIP screams misfortune.

On the FIP scale, a 4.00 is considered the mean, with a 3.30 or lower considered good and anything above 4.30 as deficient. Matt Harvey led baseball with a 2.00 FIP last season, which hovered around his 2.27 ERA (if anything, this indicates Harvey was better than we believed). However, Hisashi Iwakuma’s 3.44 FIP was significantly higher than his 2.66 ERA, meaning Iwakuma’s figures were somewhat a product of luck.

On-base plus slugging (OPS)

The equation is in the namesake, as a player’s on-base percentage is added to his slugging percentage to get this metric. Important figure as it accounts for plate discipline, contact ability, and power. In 2012, major-league average for OPS hovered around .725, with .850 and above considered commendable and anything below .680 to be poor. Miguel Cabrera led the league with a 1.078 figure.

Unfortunately, this stat is not considered the best of barometers, as it’s been determined that OBP is nearly twice as important in association to run production as SLG; alas, this equation treats both factors as equals. Because of this, a metric called adjusted on-base plus slugging (OPS+) is considered a better gauge of a player’s value, as it also takes park factors into consideration.

Nevertheless, because of its simplicity, OPS is the wider known and more commonly used statistic.

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