It’s often said that hope springs eternal in March, but even the most optimistic baseball fan knows better than to get excited by a gaudy record for the home team in spring training.

Between the muddy fields of Florida, the dry air of Arizona, the splits quad games, the pitchers’ raw arms, the preponderance of rookies, and the celebrity cameos, the Grapefruit and Cactus Leagues rarely provide an accurate picture of where a team is going. Last season, for example, four teams – Minnesota, Seattle, Montreal, and Milwaukee – finished with a .600 record or better in the spring. The Twins went on to reach the playoffs; the other three combined for a 197-288 regular-season record.

The same is true of individual players, for whom 40 or 50 at-bats against uneven competition say little about their abilities. Yet critical roster decisions are made each year based on spring performances.

Managers are sincere when they say that a particular position is up for grabs – even if one or the other candidate has a better track record, the one who performs better in the exhibition games will often emerge with the Opening Day job. The 2004 Yankees, you’ll recall, made Enrique Wilson their starting second baseman based on his torrid spring hitting, only to reverse course midseason and give the job to Miguel Cairo.

Had the Yankees consulted the players’ history, they might have inserted Cairo in the starting spot right away – according to Baseball Prospectus’s Pecota system, which projects a player’s performance based on his career statistics, Cairo was likely to be the better hitter in 2004, with a projected OPS of .715 to Wilson’s .638. As it turned out, Cairo (.292 AVG/.346 OBA/.417 SLG) markedly out-hit Wilson (.213/.254/.325) during the regular season.

Similarly, Michael Tucker and Dustan Mohr squared off last March for the starting right-field job in San Francisco. Mohr’s track record indicated that he would the better hitter – Pecota projected a .760 OPS to Tucker’s .709 – but Tucker had a notably better spring. When the season began, Tucker received the lion’s share of playing time, though Mohr outperformed him when healthy, with a .274/.394/.437 batting line against Tucker’s .256/.353/.412.

It’s no secret that the Giants give the benefit of the doubt to veterans, and their stubborn allegiance to Tucker cost them a few runs during the regular season. Given that the N.L. West race went down to the last weekend of the season, it’s not a stretch to say overusing Tucker – both in tapping him over Mohr and in not upgrading at the trade deadline – may have cost the Giants the division title.

Spring training statistics are generally not a better predictor of performance in the upcoming season than the longer arc of a player’s career. Teams like the Yankees and Giants would have done better if they had focused on the Pecota projections rather than Grapefruit or Cactus League performance. That said, there are certainly circumstances where spring performance can be a useful tool for evaluating a player’s credentials.

First, spring training results may be meaningful when evaluating up-and-coming players. For example, Khalil Greene of the Padres went into last spring competing with Rey Ordonez for the shortstop job; the rookie performed so well that Ordonez left camp. Greene’s spring was indeed an indicator of a potential breakout, as Greene had a fine debut season (.273 AVG/.349 OBA/.446 SLG) and looks like a cornerstone player. More famously, Albert Pujols’s stellar debut in 2001 was preceded by an excellent exhibition season. Because young players tend to improve at a faster rate than established players, it is sensible to pay a little bit more attention to their spring performances.

Spring training results can also be meaningful for determining how a player might adjust to a new position or role, as well as to confirm a hunch. When Jaret Wright emerged from the bullpen to compete with three others for the final spot in the Braves’ rotation last spring, he performed just well enough to win the job, posting a 4.57 ERA and a 17/6 strikeout-to-walk ratio in five starts.

The Braves had liked what they’d seen of Wright late in the 2003 season, and the spring gave them no reason to change their minds. Wright turned out to be one of the most pleasant surprises in the league last season, staying healthy and pushing the Braves toward another pennant with a 3.29 ERA. This spring, Atlanta will be watching John Smoltz in the same vein. Similarly, spring training results may help teams evaluate players recovering from injury, as the Yankees hope to do with Jason Giambi.

While it’s generally a bad idea for teams to rate one player over another based on spring stats, an extremely bad spring performance may be indicative of undiagnosed injuries or other troubles. When Edwin Jackson and Wilson Alvarez did battle over the Dodger’s final starting spot last spring, Jackson struggled with a 9.28 ERA in seven appearances, while Alvarez pitched well and emerged with the job. Jackson’s spring training troubles were a sign of things to come, though, and he performed poorly in both Los Angeles and Triple-A while struggling with a forearm injury. Playing it safe with Alvarez (4.03 ERA in 120.7 IP in 2004) might have helped the Dodgers win a close division race against the Giants.

But perhaps the most important lesson of all is that spring training battles are usually a sign of organizational distress, rather than depth. The position often remains in turmoil for the entire season, requiring a solution from outside the organization to fix. Look no further than last year’s Mets and the five scrubs they gathered to fill the final two rotation slots – Scott Erickson, James Baldwin, Jeremy Griffiths, Aaron Heilman, Grant Roberts, and Tyler Yates.

Baldwin had the best spring, giving up just one run in 12 innings, with Erickson, Heilman, and Yates also performing reasonably well. Griffiths bombed in one appearance before be ing sent to minor-league camp; Roberts pitched well early in camp, and poorly late. Erickson and Yates were named the starters once camp broke, with Roberts making the team out of the bullpen.

The result? All six pitchers had poor seasons. Erickson and Baldwin were eventually released, Yates demoted, Roberts disabled, and Griffiths traded. Heilman spent the vast majority of the year in Norfolk.

A spring position battle featuring players like these frequently deters an organization from looking for much-needed outside help. Had the Mets signed another legitimate starter last winter, rather than throwing darts with veterans like Erickson and Baldwin, they might never have made the disastrous Victor Zambrano-for-Scott Kazmir trade in July.

The more news that that your team is making in March, the less it is likely to be making in October. Teams would do well to take that to heart this spring.

Mr. Silver is a writer and editor for Baseball Prospectus. For more state-of-the-art baseball analysis, visit www.baseballprospectus.com.