Glossary

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GLOSSARY
OPS — on-base plus slugging

  • Formula: OBP + SLG
  • Basics: OPS combines two basic measures of offensive production — getting on base and moving runners over. OPS correlates extremely well to run scoring, better than either OBP and SLG alone. On the down side, OPS lacks meaning — why should OBP and SLG be added together? What does it represent? I prefer to see both OBP and SLG, but listed separately.
  • Baselines: 2007 league-average OPS is .750. Vlad has a career .970 OPS. Ted Williams has the highest non-Bonds/Ruth season OPS at 1.288.
  • Advanced: OBP is more important than SLG and should be weighted more heavily — try 1.8*OBP + SLG. Or you could use GPA, which is (1.8*OBP + SLG)/4 to put weighted OPS on the same scale as AVG.
  • See also: OPS+, OBP, SLG, GPA
  • Links: Patriot’s rant, how runs are created series, Tango on OPS, current leaders
  • Rating: 3 stars

SLG — slugging percentage

  • Formula: TB/AB
  • Basics: SLG measures a player’s ability to advance himself when he bats (and somewhat implies how far baserunners advance). It’s a decent measure of power.
  • Baselines: 2007 league-average SLG is .420. Vlad has a career .580 SLG. Barry Bonds and Babe Ruth are the only players to slug over .800 in a season.
  • More info: High-average singles hitters without a lot of power can still post impressive SLG numbers. For a pure power metric, see ISO. Walks do not count towards total bases, and thus do not help SLG. If you see a set of three numbers separated by /’s like this — .270/.330/.450 — it’s usually AVG/OBP/SLG. SLG treats all bases as equal, when in reality the first and last are more important.
  • Related terms: ISO, OPS
  • Interesting links: current leaders
  • Rating: 3.5 stars

S-N W/L — support-neutral wins/losses

  • Basics: Assigning traditional Wins/Losses to pitchers is a poor measure of anything useful. Wins/Losses are binary — you earn one or you don’t — even though a starter could perform in numerous ways. Second, many factors outside of a pitcher’s control affect whether they earn a win or not: run support and bullpen support, most importantly. Support-neutral wins and losses remove those two problems and represent the likelihood that a pitcher with a specific line (6.1 IP, 2 ER, runner left on 3rd, for example) would earn a traditional Win or Loss. In the example, the pitcher might be credited with .6 S-N Wins and .15 S-N Losses. Over a season or career, S-N Wins/Losses are on the same scale as traditional Wins and Losses, but are a much more accurate measure of performance.
  • Advanced: While S-N W/L are bullpen- and offensive-support neutral, much still lies outside a pitcher’s control — fielding, quality of hitters faced, and statistical variation of BABIP, HR/FB, etc. It’s better to judge a pitcher based on specific skills over longer periods of time (see peripherals). Also note that this definition of Win is not the same as a team win. Pitchers can be measured by how much they contribute to their team winning, but the traditional Win stat and its cousins measure something different. S-N Wins are often referred to as expected wins or E(W).
  • Links: current leaders, bullpen support, all-time list
  • Rating: 3.5 stars

VORP — value over replacement player

  • Formula: you don’t want to know (if you do, see link below)
  • Basics: VORP represents how many runs better a player is compared to a scrub at the same position, given the same playing time and park adjustments. A rightfielder must be a much better hitter than a shortstop to accumulate equal VORP, for example, because it’s more difficult to find decent fielding shortstops than rightfielders. Players deserve credit for the runs they contribute above replacement level, because it’s easy and cheap to field a team of all replacement players.
  • Baselines: In today’s game, 10 additional runs are worth about 1 win. In 2006, Derek Jeter and Ryan Howard both had 80 runs of VORP. Barry Bonds had 145 VORP in 2001, while the 90th best hitter had 23 VORP.
  • More info: Keith Woolner created VORP, and it’s now Baseball Prospectus’ baby. It has many fixable flaws, such as setting the replacement level too low and not including baserunning other than SB/CS. VORP for pitchers is a measure of runs prevented; starters have a worse replacement level than relievers. Sometimes a reference to VORP is for the concept in general, not Baseball Prospectus’ stat specifically. The sum of a team’s players’ VORPs is less than its total runs scored, because even a team of replacement players would score a moderate number of runs.
  • Related terms: replacement level, WARP, value
  • Important links: current leaders, Woolner’s rep level, Woolner’s formula, problems with VORP
  • Rating: 3 stars for BPro, 4.5 stars for the concept in general

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