Weighted Runs Above Average (wRAA) measures the number of offensive runs a player contributes to their team compared to the average player. How much offensive value did Evan Longoria contribute to his team in 2009? With wRAA, we can answer that question: 28.3 runs above average. A wRAA of zero is league-average, so a positive wRAA value denotes above-average performance and a negative wRAA denotes below-average performance. This is also a counting statistic (like RBIs), so players accrue more (or fewer) runs as they play.
Calculating wRAA is simple if you have a player’s wOBA value: subtract the league average wOBA from your player’s wOBA, divide by the wOBA scale coefficient (1.26 for 2011), and multiply that result by how many plate appearances the player received.
wRAA = ((wOBA – league wOBA) / wOBA scale) × PA
You can find “wOBA scale” values for any year from 1871-2010 here, and league-average wOBA for every year can be found on the FanGraphs leaderboards. The exact wOBA scale value varies on a year-to-year basis in order to set wOBA on the same scale as league-average OBP. Also, if you’re feeling ambitious, it’s possible to calculate wRAA using linear weights.
Please note that the following chart is meant as an estimate. No matter the year, this statistic will always have 0 wRAA as league-average.
Things to Remember:
● wRAA is league adjusted, meaning you can use it to compare players from different leagues and years.
● When calculating Wins Above Replacement (WAR), wRAA is used to represent offensive ability. Ten wRAA is equal to +1 win.
From FanGraphs Sabermetrics LibraryShare: