We love numbers here at DRaysBay. That's obvious. My favorite statistic we use is a little something called Wins Above Replacement, or WAR, and I'm here to tell you about it's exceedingly high level of awesomeness.
First, there's no other metric that acts as a unifier between many of the other advanced statistics. Things like FIP, xFIP, and wOBA, while great in their own right, are used on a micro level while WAR looks at a player's value on a more macro level. As Big League Stew's Alex Remington puts it:
WAR is a sum of the win value of a player's offense, defense, pitching, adjusted for that player's defensive position, playing time (thus keeping the replacement level players off the field) and year, park, and league context
You should never use just one statistic to judge a player's worth, but if you had to pick one WAR would likely be your be your best bet.
Secondly, WAR allows you to easily compare players' worth. Who doesn't love comparing players? WAR is expressed in wins, i.e. player X was worth 5.5 wins last year while player Y was only worth 3.0. It's quick, and at it's core very simple way to say one player is better than another while providing statistical evidence.
Lastly, WAR can shed light on just how good a player as been. Meaning that we all knew Ben Zobrist was having a fantastic season in 2009, but without WAR we wouldn't know just HOW fantastic it actually was. His amazing versitility and break out offensive season lead to a 8.3 WAR that ranked first among AL hitters. While WAR certainly helps showcase a lesser known player's talents, it can be used to accentuate a star's skills as well. Let's take the Rays most beloved player, Carl Crawford, as our example.
It's no secret that Crawford is having arguably the best season of his career. It's not until you dig a little deeper that you realize just how good his first half has been. Currently Crawford is ranked second in all of baseball in WAR with 4.8, just behind the 5.0 of leader Justin Morneau. These are his current figures:
Batting: +22.9 runs
Fielding: +15.2 runs
Replacement: +12.4 runs
Positional: -3.7 runs
As our own Steve Slowinski points out in the SaberLibrary, those numbers aren't based against the league average, but on "...replacement level (which...is the value a team would lose if they had to replace that player with a minor leaguer or someone from the waiver wire). Convert the run value you have to wins (10 runs = 1 win) and voila, finished!" Crawford excels with his bat and glove, but is penalized because of the relative ease of left field. If he played center field I have little doubt his WAR would be higher than Morneau's.
To recap, WAR is a fantastic, quick and easy tool to use when evaluating a player's worth that also gives you a solid base when comparing different players. WAR, as it turns out, is good for quite a lot.
*All data is from FanGraphs' WAR calculations. Baseball-Reference also has WAR but uses a different defensive measurement than UZR.