Wins Above Replacement (WAR): perhaps the most controversial advanced metric because a good number of writers and commentators have decided to use it as the be-all, end-all baseball statistic. It is designed to be a single number that represents how many additional wins a player’s team could expect to gain from that player’s presence as opposed to a “replacement” player from the minor leagues. A player whose statistics yield 5 “wins” above replacement would typically be considered an All-Star and a player with a WAR of 8 or higher would be an MVP candidate. It’s a statistic that’s easy to understand in terms of its meaning but difficult to comprehend in terms of how it’s calculated. Think of it as the “passer rating” stat of Major League Baseball. For decades, we’ve been told about a quarterback’s passer rating without understanding the math behind it. We just know its important and trust it.

One key thing to understand about WAR is that it is a counting stat, not a rate stat. The more years you play, the higher your WAR is likely to be. This is different than stats like Batting Average and ERA where a player can start going downhill in the later years of their career. WAR is, however, a counting stat in which you can count backwards. Some players, still on the field late in their career due to reputation, are actually playing at such an inferior level that their WAR is below zero. Hall of Fame first baseman Eddie Murray is a recent example of this. In his final two seasons, bouncing from Cleveland to Baltimore to Anaheim to Los Angeles, Murray had a woefully low .711 OPS, which resulted in a WAR of minus 1.3  Still, in most cases, you’re going to have a higher WAR just by playing longer.

The one great benefit of WAR is that is the one and only statistic in which you can actually compare position players to pitchers. Needless to say, the way that its calculated for batters and pitchers is entirely different. Here’s the basic methodology:

WAR for Position Playersthere are six components that make up WAR for a position player. If you’re a rocket scientist, a fully detailed breakdown of how these components are calculated can be found here on Baseball Reference. For the rest of us, this will help us understand how the numbers add up.

  • Rbat (WAR Runs Batting): for each position player, this number represents the number of runs above or below average a hitter is. Since this number is compared to an “average” MLB player (not a replacement level player from the minor leagues), many hitters will be in negative territory here. There are, in fact, a full 10 Hall of Fame position players who are negative in “Runs Batting.” This doesn’t necessarily mean that these were bad Hall of Fame selections (Ozzie Smith is one of the ten) but it does mean that they’re in the Hall because of their fielding or running ability.
  • Rfield (WAR Runs Fielding): this number represents the number of runs above or below average a position player was in the field. Again, this number is compared to an average MLB player so many players will be negative here. Of the 153 position players in the Hall of Fame through the class of 2017, 41 of them were defensive liabilities to some degree. This isn’t that stunning because we all know that a great many hitters are in the Hall because of their prowess with the bat, not the glove. Rfield is the most controversial of the WAR components because of some shocking numbers. For instance, the numbers say that Roberto Alomar (owner of 10 Gold Gloves at 2nd base) was minus 36 runs as a defensive player. This is the statistic that people cite to say that Derek Jeter is the worst defensive player in the history of baseball. He’s not the worst, really, because most truly awful defenders couldn’t hit nearly well enough to accumulate over 11,000 plate appearances. My own feelings about Rfield is that it should be considered fairly reliable after the year 2003 (when Baseball Info Solutions introduced “Defensive Runs Saved”) but, for years prior, should be viewed upon with a level of skepticism.
  • Rbaser (WAR Runs Baserunning): this represents the number of runs above or below average a player was on the base paths. It includes stolen bases, times caught stealing but also the number of extra bases taken and outs made on the basepaths. An Extra Base Taken (XBT) is defined as going from first to third on a single or first to home on a double. An out on the basepaths defines itself.
  • Rdp (WAR Runs Grounding into Double Plays): because a double play is a uniquely damaging out, it has its own category. It’s a small subset of hitting situations so its impact on a player’s overall WAR is less here than it is for Rbat, Rfield or Rbaser but it still can be significant. Because its easier to turn double plays on balls hit to the left side of the infield, right-handed batters tend to ground into double plays more often. The bottom seven Rdp members of the Hall all swung the bat from the right side.
  • Rpos (WAR Runs from Positional Scarcity): this is an adjustment based on the defensive position occupied by each player. It’s an old baseball adage that you have to be “strong up the middle” (the “middle” being catcher, 2nd base, shortstop and center field). Rpos takes this into consideration. This is a subjective component in what is otherwise an objective methodology. The number of added or subtracted “runs” by positional adjustment is somewhat arbitrary. Making this more complicated is the relative importance of defensive excellence at different times in history. In today’s game, defense is less important than ever because so many more at bats end in strikeouts or walks than ever before. Rpos does take this into account. The positional adjustment is, in most cases, less today than it was in yesteryear.
  • Rrep (Runs from Replacement Level): this is simply the level of additional runs that a player is expected to be than a replacement level player based solely on playing time. This is based on plate appearances only, not by position. It’s based on the concept that being able to suit up every day is worth something. It’s the one component of WAR that has only positive numbers, no negatives.

For positional WAR, you can go to Baseball Reference and add these six components to get “Runs above Average” (RAR), the basis from which WAR is calculated.

Offensive WAR (oWAR): this takes all of the elements of a position player’s Total WAR but excludes defense. It includes batting, base-running, DP avoidance and also has the positional adjustment. If you don’t trust the defensive metrics, you can look at oWAR to simply see how valuable a player was on the offensive side of the game.

Defensive WAR (dWAR): this takes only the player’s defensive contributions and positional adjustment into account in a WAR calculation.

NOTE: if you add oWAR and dWAR together it will NOT get you a player’s overall WAR because it would take in the positional adjustment twice.