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A Primer on Sabermetrics

In our April issue, we have a feature on stats that makes the case for better ways to evaluate baseball players. The alphabet soup of advanced metrics include OPS+ (Adjusted On-Base Percentage Plus Slugging Percentage), FIP (Fielding Independent Pitching), and UZR (Ultimate Zone Rating) — and they’re likely to give you a headache. But don’t worry! Some kids in the HeschelSABR Club in New York have your primer on some key sabermetrics you need to know to be a better fan.

1. WAR (Win Above Replacement) is by far the coolest name on this list. But it’s also a key advanced metric. It counts how many wins a player adds to his team’s total compared to an average replacement. While not a perfect stat by any means, WAR is becoming more and more popular. This year, both Mike Trout and Clayton Kershaw, the AL and NL MVPs, led their league in WAR.

2. wOBA (Weighted On-Base Average), while falling just short of the top of our rankings, is an equally useful tool for measuring a hitter’s worth. It does this by assigning a value to every way a hitter reaches base using his own skill. So, it counts walks and hit by pitches but not errors.

3. The problem with traditional pitching statistics has always been that they are heavily influenced by how good a pitcher’s defense is, even if errors aren’t counted. FIP (Fielding Independent Pitching) tries to take defense out of the picture by only using things that a pitcher can control: home runs, walks, hit-by-pitches, and strikeouts. One pitcher who clearly shows FIP’s worth is Rick Porcello, formerly of the Tigers. He had a 4.32 ERA in 2013, but a very strong 3.53 FIP. Predictably, in 2014, his ERA dropped to a much better 3.43.

4. When a hitter suddenly breaks out and hits better than he ever has before, it is easy to assume that he has just improved as a player. But it’s also possible that he has just been lucky. Unless a player suddenly starts hitting the ball harder, his BABIP (Batting Average on Balls In Play) usually stays the same. If it is higher than usual, his hot streak is probably a result of luck, and will end quickly. For example, in 2013 Atlanta’s Chris Johnson had a great batting average of .321 and an astronomical BABIP of .394. Last season, his BABIP fell to a more reasonable .345. His batting average last season? A not-great .263, which was a huge drop-off from 2013.

5. SIERA (Skill Interactive ERA) is another pitching stat that attempts to discount defense. Unlike FIP, though, it doesn’t totally disregard balls that are put in play. Itoperates based on the assumption that when it comes to balls in play, a pitcher should stick to what he is good at. This means that a ground ball pitcher is less likely to give up a hit on a ground ball, and a fly ball pitcher is less likely to give up a hit on a fly ball. Therefore, if a ground ball pitcher is giving up a lot of ground ball hits, it’s probably because there is a bad defense playing behind him. Last year, Brandon McCarthy had a very mediocre ERA of 4.05, but a very solid 3.00 SIERA. This means that we can expect him to have a much lower ERA in the coming season.

6. The first exclusively defensive stat in these rankings, UZR (Ultimate Zone Rating) combines every aspect of an individual player’s defense to make one all-encompassing number that measures how much better or worse a player was on defense than an average defender. Last year’s leader in UZR was Alex Gordon of the AL-champion Royals.

7. Although slugging percentage favors power hitters, it’s still possible to have a high slugging percentage while hitting a lot of singles. In order measure only power (extra-base hits), sabermetricians subtracted batting average from slugging percentage to create ISO (Isolated Power). The league leaders in this stat are usually hitters with relatively low batting averages but who hit a lot of home runs. Case in point: Edwin Encarnacion had the highest ISO in the league last year. 

8. While OPS (On-Base Plus Slugging) adds on-base and slugging percentages and has been widely used, it can easily be affected by where a hitter plays his home games. For example, a player who plays in Coors Field in Colorado has an advantage over one who plays in cavernous Safeco Field in Seattle. OPS+ (Adjusted On-Base Percentage Plus Slugging Percentage) is just like OPS, except it adjusts for this advantage. Additionally, it adjusts for the conditions of the league at any time, meaning that we can compare a player from today, like Robinson Cano, to a player from the 19th century, like Cap Anson. In case you’re wondering, Anson’s OPS+ in 1888 was 176, while Cano’s career high is 148 (100 is average).

9. wRC+ (Weighted Runs Created) is an attempt to quantify how many runs a player contributes to his team relative to an average player. This number, similarly to OPS+, is adjusted for the time period and the ballpark. Last year, Carlos Santana only had a .231 batting average, but his 130 wRC+ revealed that he was actually a very good player.

10. Another defensive stat, Defensive Runs Saved (DRS), shows how many runs a player saves or gives up for his team relative to a league average player. In order to do so, it looks at each individual type of play made by a fielder and evaluates how many other players in the league would have made the play. It also allows us to measure each individual aspect of a player’s defense. For example, we can see that YoenisCespedes had the best arm in the league, but was hurt by a lack of range.

Sabermetrics reference guide organized by the SABR Club at Abraham Joshua Heschel School in New York. Definitions and rankings compiled by Max Mannis, Max Melamed, and their teacher BosiKinar.

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Photos: Seth Wenig/AP (graph), Otto GreuleJr/Getty Images (Trout), Ralph Freso/Getty Images (Kershaw), Mitchell Leff/Getty Images (Porcello), Orlin Wagner/AP (Gordon), Jason Miller/Getty Images (Santana)