Who was a better baseball player, Frank Thomas or Ozzie Smith? I can imagine many different viewpoints arising from that one. You might suggest that the players are apples and oranges; not easily compared and maybe not worth comparing. Wins Above Replacement (WAR) was designed to take players of all different positions and all different skill types, and compare their overall outputs in a clean, practical way.
What WAR is…
WAR is an all-in-one stat that has been created by the resident nerds in the sabermetics baseball community. You might say that the “unit” for WAR is how many wins a player creates for his team, from his performance alone. It’s purpose is to compare the value of players from different positions, teams, leagues, seasons, eras, and so on, and to do so with one comprehensive metric that puts all players on an even grading scale. Because of the nature of baseball and the subtle role of human subjectivity built into the equations for calculating WAR, there are limitations to the stat. However, because of adjustments included in the calculations, WAR is able to account for the differences in playing in different ballparks, in the American vs. National league, and in the different realities of different baseball eras (steroid era, different ball densities, different mound heights, etc.). This sort of stat “neutrality” that WAR maintains is very important, and is generally more than can be said for traditional baseball statistics (batting average, ERA, RBIs, etc.). So, WAR provides us baseball hacks with a very useful method for calculating the contributions of different players, even if those players bring very different skills to the table, and/or played in very different circumstances.
What WAR is NOT…
WAR is not intended to be an exact description of everything that a player has done, but rather a reliable estimator of a players value so far. The stat is cumulative, which means it “grows” as the season progresses. In other words, a player who is batting .400 after the first week has a tiny WAR value, but a player with a .400 average at the end of a full, healthy season would have a huge WAR value. WAR is about how much value you have accumulated over a season via your performance. Because of this, the stat is subject to things like injuries and other playing time effects, how the rest of a player’s team is performing offensively (lineup “protection”), and luck and general streakiness. So, if we really want to tell the whole story about a player’s production we have to dig deeper, using multiple stats and sometimes less mathematical considerations.
War is also not intended to measure what a player CAN do. We can’t look at a player who just had a low WAR season and say, “whelp, that player stinks and that’s the end of it.” A player’s WAR value tells us only the value of a player’s performance in a given season. As always, we can feel more confident in using WAR to assess how talented a player is overall when we have a larger number of seasons worth of data to use. But again, to see the whole story, we need to consider with WAR things like age and stage of development of the player, injuries, playing time, etc. when we use WAR to assess the talent of a player.
How is WAR calculated?
The WAR calculation is simpler than it may sound, but it does involve many factors. There are actually two versions of WAR, one created and calculated by FANGRAPHS (fWAR) and one by Baseball Reference (bWAR or rWAR). Let’s get the big picture here, and then lean on the detailed work of the experts to further explore the wonky details as desired.
First of all, it’s important to note that WAR is calculated in very different ways for Hitters and Pitchers. Hitters are graded on their Hitting, Base Running, and Defense, which is all combined and represented in their WAR value. Pitchers are graded purely on their pitching outcomes. Also of note, the defensive contributions of catchers are graded differently than that of other positions because of the uniqueness of the defensive demands of catching. However, though the nature of being a catcher, pitcher, infielder or outfielder varies quite a bit, WAR values of all players are all molded to represent the same thing: how many wins your performance is worth, compared to the performance your team would get from a Replacement-level player, or an average Triple-A or bench player. To add some clarity to that last sentence, let’s explore (1) the concept of measuring performance in Wins, and (2) the nature of the Replacement-level player, the two of which really make up the meat and potatoes of what WAR is claiming about a player.
(1) Performance measured in Wins: not to be confused with things like Pitcher Win-Loss record or game-winning RBIs, the Wins component of Wins Above Replacement is the result of some fairly complex math. We will take care to see the forest from the trees here, and again encourage readers to explore the links below for more complex details.
For hitters and pitchers, all of a player’s components of performance are converted to Runs. For Pitching and Defense, this value really means runs prevented. For Hitting and Base Running, this indeed means Runs created. [Note: the methods used to convert different performances to Runs introduce the complexity and subtle human subjectivity of the WAR calculation mentioned above.] These Runs are then converted to Wins. This involves some of the year-to-year adjustments I mentioned about WAR. From year to year, Wins “cost” more or less Runs depending on the run scoring environment of that season. In a year where more runs are scored overall, teams need more runs to earn a win, so a Win “costs” more Runs.
This is also a good time to give context to League and ballpark adjustments: there are small adjustments to a player’s Runs created/prevented numbers depending on if he plays in a ballpark or league where runs are relatively easy or hard to come by. This is to make sure that players are not penalized are rewarded for things that are out of their control. For example, pitching is relatively difficult and hitting relatively easy in Denver for the Rockies. To keep all players on an even grading scale, the pitcher is penalized less for giving up Runs than is a pitcher in a more hospitable ballpark, and the hitter is rewarded less for Run creation than is a hitter in a less hospitable ballpark.
One last adjustment to consider is that of defensive position. This one is a little abstract, so I’ll be brief to keep the focus on the big picture. Shortstop is more difficult to play than Right Field…. so, the contributions of a Shortstop are adjusted to be worth more Runs than that of a Right Fielder. The basic idea is that it’s more difficult to find a player who can hold down SS and create Runs offensively than it is to find a RF to create that production. So, the production of a SS is more valuable to the player’s team. This difference in value is reflected via small adjustments in Run values for players of different positions, which then affects their overall WAR values. Here’s two links to more on defensive position adjustments for WAR, here and here.
(2) The Replacement-level player: a much simpler but still abstract element of WAR is the imaginary, average Triple-A, or backup player, against which WAR compares all players. That didn’t sound simple at all… this will: WAR uses a combination of projections and historical data to determine the value of the average non-impact baseball player. We’re talking about a guy who doesn’t really hurt his team, but brings no competitive advantage. An on again, off again Triple-A call-up, or the non-valuable bench guy who is really just there for depth. WAR then uses the determined value, in Runs, of our imaginary non-impact (but still rich!) player to compare all the actual players to. After we calculate for a player how many Runs better than Replacement-level production he is, we convert those Runs to Wins and voila, you have that player’s WAR.
In conclusion, WAR is a great tool for comparing different players in terms of how valuable to their teams their production is over the course of a season. The stat has it’s complexities and human decisions built into it, but every component of the stat is based on data trends that range in size from many seasons to more than 100 seasons. Use WAR for its convenience, it’s well-conceived method of measuring player performance in Wins, and its neutrality across different leagues, ballparks, and seasons. Also, make sure that WAR is only your starting point if you want to see what a player is really bringing to the table.
You can find WAR values used and listed in many different places on the web. You can explore WAR and a mind-boggling array of other sabermetics, for players and teams over many seasons at FANGRAPHS and Baseball Reference. Those two sites also feature great saber-minded writing by a bunch of great writers, as do the indispensable Beyond the Boxscore and The Hardball Times. Enjoy.
More depth on WAR from FANGRAPHS