The stat is just one of the many categories that have sprung from the sabermetric movement, which looks beyond traditional box score stats such as batting average, stolen bases and RBIs to rate a player's worth to his team.
According to the Society of Baseball Research, "sabermetrics" was coined by baseball historian and statistician Bill James to mean "the search for objective knowledge about baseball." James' analytical writing revolutionized the approach to the game in the 1980s, and his ideas have been gaining ground on the traditionalists' game.
"The dialogue has changed over the last few years," said outfielder Sam Fuld, a longtime fan of analytical baseball statistics who now happens to play in Oakland -- the locus of the movement. "Not a ton, but even as short as five years ago, if somebody brought up WAR, there wouldn't be too many people who would understand it. Nowadays, I think everybody here has at least a good sense of what WAR is and a lot of the other advanced metrics. It's a subtle change, so it's not something that we talk about on a daily basis, but you definitely hear it thrown around more often."
Perhaps the biggest step forward for the sabermetrics occurred in 2003 with the publication of Michael Lewis' "Moneyball: The Art of Winning an Unfair Game," which became an award-winning film in 2011. The story centered around the 2002 Oakland Athletics and general manager Billy Beane, who figured out a way to win with the second-lowest payroll in baseball.
As the book explains, Beane and his front-office staff utilized James' statistical approach, going against traditional scouting views. They employed undervalued players with a focus on hitters that could get on base at a higher clip and pitchers that had high ground-ball rates.
With the sabermetric managerial style -- and truth be told, a very solid core of young talent -- the 2002 A's won the American League West. Since "Moneyball," Beane has been linked to the advanced metrics philosophy.
Though they hit a dry spell from 2007-11, the A's are back to their winning ways, having claimed the AL West title the past two seasons.
And they are doing it with the fourth-lowest payroll in the league, $76.6 million, competing in a division against the big-spending Angels ($146.6 million) and Rangers ($126 million).
"That's part of what drew me over here," Fuld said. "Not necessarily their link to sabermetrics, but just that they're a smart organization, and that's appealing to me.
"It was always something that was intuitive for me -- whenever you can use data in the correct way, it can be helpful. It's cool that this organization is one of the first to employ the use of advanced metrics, and it's also nice to see so many other organizations following suit. I think as long as you're using those numbers in the correct way and you understand what you're looking at, then I think it's a no-brainer to use them."
For Fuld, he likes that sabermetrics are placing more value on the defensive side of the ball, a part of his game that he takes pride in.
Fangraphs.com, an advanced metrics website, lists 20 defensive categories, not to mention the 60-plus offensive and pitching stats that cover anything from how often a batter swings at balls out of the zone to the percentage of fastballs thrown by a certain pitcher.
All these stats are available for players and fans alike, and while the collection may be a statistician's dream, for some players it can be too much.
"I think that there's sometimes knowledge overload where we overthink things," A's catcher Stephen Vogt said. "It's nice to know that a guy might throw a fastball 60 percent of the time, but at the end of the day, you still have to hit it. You can know a pitch is coming and still swing and miss at it because of how good it is."
Stats can only tell you so much, and ultimately, computers are not the ones playing the game. The numbers often can't account for in-game adjustments made by players.
"I know [sabermetrics] are important and they're a big reason why I have a job, but as a catcher, I know that in the game I'm looking for my pitcher's strengths and the hitter's weaknesses," Vogt said. "At the end of the day, a slider in one situation -- just because 'sabermetrically' a guy might hit it -- it is still the right pitch."
Fuld echoed Vogt's stance on advanced metrics when looking at them from a player's perspective. Baseball is all about the process, according to Fuld, and if one becomes too caught up in the numbers, it can be detrimental to a player's approach to the game.
"I've found that the less you can look your stats throughout the season the better," Fuld said. "But I think at the end of the season, whether good or bad or in between, it's helpful to look at [the metrics] to get a better idea of where you can improve.
"If anything, they are just an interesting way to look at the game."