fWAR and rWAR

During 2010, Baseball-Reference unveiled a new feature: current and historical WAR values on each of its player pages. This WAR (referred to as rWAR) uses the same framework as FanGraphs’ version (fWAR) — in that it attempts to encapsulate a player’s total value to their team in one stat — but has three main differences:

● Pitcher Value. fWAR uses FIP to calculate WAR for pitchers — making it defense independent — while rWAR takes a pitcher’s actual Runs Allowed and adjusts that to account for their opponents, team defense, park, and role.

For more on why we believe FIP is the best metric to use when calculating WAR, see the Library page on Pitcher WAR values.

● Calculating Defense (2002-Present). For recent seasons, each system uses a different defensive metric. fWAR uses UZR, while rWAR uses Total Zone. UZR is considered more accurate, but is only available from 2002 onward, while TotalZone values can be calculated for any player in baseball history. As such, fWAR uses UZR for every year from 2002 onward, and it uses Total Zone for earlier seasons.

● Baserunning. Both rWAR and fWAR includes base running, although they use different metrics. fWAR uses Ultimate Base Running (UBR) & Weighted Stolen Base Runs (wSB), while rWAR uses their own linear-weights-based system.

Until early 2013, it used to be that another significant difference between the two systems was that each calculated Replacement Level differently. That has since been changed, and both sites now calculate replacement level the same way:

This new unified replacement level is now set at 1,000 WAR per 2,430 Major League games, which is the number of wins available in a 162 game season played by 30 teams. Or, an easier way to put it is that our new replacement level is now equal to a .294 winning percentage, which works out to 47.7 wins over a full season.

As a result of the differences listed above, rWAR values typically come in lower than fWAR values, meaning a 6 rWAR is more impressive than 6 fWAR. But it’s worth noting that the two systems are more alike than they are different, and that their different calculations should be viewed as a feature, not a bug.

Links for Further Reading

Introducing rWAR – Baseball Reference

How Much is Fielding Weighed in WAR? – FanGraphs