From SABR member Rob Arthur at FiveThirtyEight on September 21, 2015:
As MLB award season arrives, no prize looms larger than Most Valuable Player. From a statistical perspective, the best guide to the MVP award is undoubtedly wins above replacement, and some voters develop their MVP ballots at least in part based on WAR. If you were going just by WAR, the American League MVP should go to the Blue Jays’ Josh Donaldson (7.1 WAR) over the Angels’ Mike Trout (6.8 WAR); while in the National League, Bryce Harper (8.0 WAR) of the Nationals looks like an obvious choice (all stats are current through Sept. 13).
The problem is that we don’t know who truly has the most WAR in each league.
WAR looks like a single easy-to-understand stat, but it’s the product of a complex model. That model integrates information on all the ways a player provides value: his hitting, fielding, baserunning and (for pitchers) pitching. The WAR you find at, say, FanGraphs or Baseball-Reference.com is an estimate of all those categories combined.
Originally published: September 21, 2015. Last Updated: September 21, 2015.