Conventional wisdom would suggest batting average, home runs, and RBIs are the most valuable offensive categories while wins/losses, ERA and strikeouts are most important for pitching candidates.
But with the emergence of sabermetrics over the last few years, baseball geeks and voters have the opportunity to delve deeper into the issue.
Rays outfielder Sam Fuld is one of those sabermetricians. Fuld graduated from Stanford armed with an economics degree and interned with STATS, Inc. He was featured on Tampa Bay's sabermetric-themed broadcast and has written for ESPN.com's Grantland. So when it comes to evaluating a player, he looks beyond those traditional categories.
"WAR," Fuld said of the Wins Over Replacement stat, which comprehensively measures a player's value to his club over a Minor League or bench replacement. "That'd be the first place I'd look. Because it's so all-encompassing, I think it's a great way to look at a player's overall value offensively, defensively and on the bases."
Of the last 20 MVPs (10 in the American League and 10 in the National League), 10 have been league leaders in WAR. But only twice in the last 10 seasons -- in 2005 with Albert Pujols and Alex Rodriguez, and 2003 with Barry Bonds and Rodriguez -- did both winners lead their respective leagues in WAR.
Bonds' MVPs came in direct correlation to his leading the NL in WAR. When he won four straight NL MVPs from 2001-04, he led Major League position players in WAR each of those seasons. He also led the Majors in his MVP seasons of 1992 and 1993, while leading the NL in his MVP season of 1990.
But if WAR were the end-all, be-all of telling statistics, Fuld's teammate and Rays utility man Ben Zobrist would have a bit more hardware. Zobrist led all position players with an 8.5 WAR last year (he finished 16th in the AL MVP voting), and led AL position players with 8.3 (he finished eighth) in 2009.
Pitchers can be evaluated by WAR, as well. In fact, historically speaking, it's easier to predict a Cy Young winner by WAR than an MVP winner. Of the last 20 Cy Young winners, 12 led their respective leagues in WAR. From 2008-10, every Cy Young winner led his league in WAR.
"I like WAR for [pitchers], too," Fuld said. "But I still think ERA is a good indicator of a pitcher's success. I guess you can look at like FIP [Fielding Independent Pitching] and the stat that's more of a true ERA that takes into account everything."
Of course, pitchers present an entirely different conversation. But it still begs the question of what statistic people pay attention to, and how in-depth voters look. Not all pitchers win with strikeouts, and not all hurlers -- consider closers -- rack up innings or victories. Some players, on mediocre teams, find their way to a lopsided record despite having the credentials in plenty of other categories.
Tim Lincecum, who won the NL Cy Young in 2008 and 2009, led the league in strikeouts both those years and also paced the NL competition in strikeouts per nine innings. He believes that was a determining factor.
"I don't really know [what stats made the difference], because I wasn't really looking up the stats of the other pitchers," Lincecum said. "But I've always been a strikeout-category guy, which might have swayed them [the voters] one way or another."
Pirates pitching coach Ray Searage said he expects Cy Young winners to be workhorses.
"Number of innings pitched, what he's done for his team," he said. "Basically, among all the different categories, you watch the workload of a pitcher; it's somebody who pitched a lot of innings ... somebody who is going to be the most efficient pitcher out there and regularly keep his team in the game and give it a chance to win. [Felix Hernandez in 2010] didn't have the record, but I thought was deserving for what he did for his team every time out."
One of Searage's pitchers this season, A.J. Burnett, has won double-digit games in 10 of his 14 seasons, while setting a season-high with 18 in 2008 with the Blue Jays and also leading the AL with 231 strikeouts. He had 61 more Ks than Cliff Lee, who won the Cy Young with 22 wins and a far lower ERA.
"A lot of things come into play," Burnett said. "You can go either way with wins or ERA, but I would say it's the guy that's carried you the whole way, the guy who stands out the most on that one team of the year, and regularly takes them where they needed to go."
Neither Lee's Indians nor Burnett's Blue Jays were in playoff contention that season. But it leads to a variable that is almost universally agreed upon to be a factor in award considerations: team performance as it pertains to individual awards.
Last year, Ryan Braun and Justin Verlander both led their teams to playoff berths. In fact, the last MVP who did not play for a playoff team was Albert Pujols in 2008, when his Cardinals finished 11 1/2 games out in the NL Central.
"A lot has to do with the team, even if you have a sensational year, but the team really isn't doing much, ... people ... go in another direction," said Pittsburgh outfielder Andrew McCutchen, who knows all about flying under the radar due to team performance. "So team wins and its success has a lot to do with it. This is assuming several players are on a similar level as far as their own numbers."
As it stands, the NL ERA and wins leader (R.A. Dickey) does not play for a contender. Same goes for the league's RBI leader (Chase Headley) and possibly the home runs leader (Ryan Braun), who is second in RBIs. Things in the AL are a little more top-heavy, with Trout, Josh Hamilton, David Price and Miguel Cabrera headlining the chase for both hardware and the postseason.
All things considered, every voter and every fan is going to have their own opinion. And perhaps the answer to the question -- "What is the most important stat?" -- is, simply, "All of them."
"It's got to be an all-around thing," said Hamilton, the 2010 AL MVP. "I think you have to look at all categories: average, hits, runs, RBIs and home runs. Whoever does the most for their team to get them somewhere."