Offense (Off) is a statistic that combines a position player’s total context-neutral value at the plate and on the bases. Off is a combination of our park adjusted batting runs above average and our base running runs above average and credits a player for the quality and quantity of their total offensive performance during a given period of time.
While statistics like wOBA and wRC+ communicate a player’s batting performance on a per plate appearances basis, when looking for total value you want to scale those to the total number of plate appearances. Additionally, Off also includes base running value to provide you with a complete sense of the player’s offensive game.
Off is set with league average equal to zero and about every ten runs above or below average is equivalent to one extra win. If you combine Off with a player’s fielding runs, positional adjustment, replacement runs, and the league adjustment, you only need to divide by that year’s runs per win to arrive at the player’s Wins Above Replacement (WAR). If you want to know how much value a player has added on offense, Off is the place to look.
Calculating Off is straightforward, but requires a couple of steps. The basic equation is:
Off = Batting Runs Above Average + Base Running Runs Above Average
In that equation, Batting Runs Above Average are simply the park adjusted version of Weighted Runs Above Average (wRAA) and Base Running Runs Above Average is simply BsR, which is equal to wSB + UBR. The wRAA equation is as follows and lgwOBA and wOBA scale for all years are available here:
wRAA = ((wOBA – lgwOBA)/wOBA Scale)*PA
To park and league adjust wRAA, do the following:
Batting Runs = wRAA + (lgR/PA – (PF*lgR/PA))*PA + (lgR/PA – (Specific League non-pitcher wRC / Specific League non-pitcher PA))*PA
You can find lgR/PA here. PF is the team’s park factor expressed as a decimal, so 95 would be 0.95, and you can find the league specific (i.e. AL or NL) wRC and PA in the leaderboards. Please note that some of the values visible on the site are rounded, so your calculations maybe be off by small fractions of a run.
Once you have Batting Runs, you simply add that to BsR. The BsR equation is:
BsR = wSB + UBR + wGDP
Ultimate Base Running (UBR) is a base running stat that gives credit for base running plays such as taking the extra base and avoiding making outs on the bases. It is based on the run value of advancing and the difficulty of advancing. You can read more about it at the link provided. Weighted Grounded into Double Play Runs (wGDP) credits batters who avoid double plays in double play situations and penalizes those who hit into a bunch. Weighted Stolen Base Runs (wSB) is easier to calculate. The equation is here:
wSB = SB * runSB + CS * runCS – lgwSB * (1B + BB + HBP – IBB)
You can find runSB and runCS for each year here and lgwSB is calculated by doing the following:
lgwSB = (lgSB * runSB + lgCS * runCS) / (lg1B + lgBB + lgHBP – lgIBB)
Once you have calculated Batting Runs and wSB, you can add that to UBR (which is available here on FanGraphs) and you have Off, or Offensive Runs Above Average.
When evaluating a player’s performance you care about two things; their performance on an at-bat by at-bat basis and the quantity of that performance. A player with a .400 wOBA in 10 PA is less valuable than a player with a .385 wOBA in 600 PA. That’s why we use run and win value statistics when we discuss the total value of a player. It’s not just about how well you play, it’s also about how much you play.
Specifically, Off provides you with a comprehensive measure of a player’s offensive output. Want to know the difference between a .350 wOBA and +1 BsR in 500 PA compared to a .350 wOBA and +1 BsR in 350 PA? Off is the statistic for you.
How to Use Off:
Using Off is extremely easy once you learn how to interpret run value statistics more generally. In this case, league average is set equal to zero and every run above or below zero is a run above or below average. One win is equal to about 10 runs.
Given that, you can use Off to determine the value of the player in question relative to the average offensive player. If your player has an Off of about 20, you can say that he has contributed about two more wins to his team than the average offensive player during the time period in question. This value comes from the player’s hitting and base running and is park adjusted.
You want to make sure that you aren’t making too much of Off in small sample sizes, as it is subject to the same variation as the statistics that generate it. You should also not be terribly concerned about the precise value as much as the general range. A 35.0 Off player and a 34.5 Off player are too similar to distinguish.
Since Off is set with league average equal to zero every year, the following rules of thumb apply. Use these as a guide:
Rules of Thumb
Things to Remember:
● Off combines hitting and base running. If you want to evaluate them separately, use Batting (or wRAA) and Base Running (BsR) in the value section of the leaderboards.
● Off is park adjusted and gives credit for the level and quantity of a player’s performance
● League average is always set to zero.
● About ten runs of Off is equal to one win.
Links for Further Reading: