Rookies will break your heart.

As frustrating as it can be to watch teams like the Yankees and Giants damage their chances in the present and the future by refusing to give rookies playing time in even the most marginal roles, it’s not hard to understand their reasons. Minor league statistics, so promising on the pages of Baseball America, often hide crippling weaknesses like an inability to hit a breaking pitch or cleanly field a grounder.

Still, you have to break the kids in sooner or later, if only so they can one day sign a huge contract to play in New York or San Francisco. This year’s crop of Rookie of the Year candidates is one of the least impressive in recent memory, and history shows that at the end of the year it will probably not be a pair of heralded studs hoisting the American and National League Jackie Robinson Awards, but two players drawn from the pool of minor league veterans, Japanese ballplayers, and greenhorns who started the year ticketed for Double-A.

If it is a much-hyped blue chipper who wins out in the senior circuit, it will probably be one of two pitchers: Philadelphia righty Gavin Floyd, picked out of high school in the first round of the 2001 draft, or Colorado lefty Jeff Francis, drafted in 2002 out of the University of British Columbia.

Floyd is an unusual case. His minor-league statistics, while solid, don’t really match his reputation as one of the best pitching prospects in the game. In particular, he didn’t have the kind of strikeout numbers you generally like to see in an elite young starter. Of course, there are a few caveats.

The first is that Floyd was young for his leagues; he just turned 22 this January, and has only pitched 30 innings in Triple-A. Being advanced enough to rocket to the majors is often a better sign than a whole sheet of impressive numbers. The second caveat is that the Phillies restricted his use of his best pitch, a hard curve, in an attempt to make him learn how to pitch, as opposed to getting by on his stuff. I caught his first start of the season, when he gave up three hits and one run in seven innings to the Cardinals, and that curve is an impressive pitch, very hard to square up on.

Floyd should get the support he’ll need from his offense and bullpen to win enough games to figure in Rookie of the Year balloting; he just needs to learn how to pitch at the major league level. If he does, the Phillies will be in good shape in the East, and will look like geniuses.

Francis is an even trickier case. Last year, he emerged as perhaps the finest starter in the minors, and he has all the statistical markers for success. In Double-A, his 1.98 ERA was less impressive that his underlying numbers. He posted a 147/22 strikeout-walk ratio in 113 2/3 innings, and allowed only nine home runs. He was even better with the Rockies’ Triple-A affiliate in Colorado Springs, where he posted a 2.85 ERA despite pitching in an extreme hitter’s park. Francis finished the season with seven competent starts for the Rockies, including a 2.46 ERA in two starts at Coors Field.

The problem for him, of course, is that the effects of Coors Field go far beyond inflating ERAs. The thin air affects the break on pitches; muscles tire more quickly and heal more slowly at elevation; pitching there requires a style much different than one that will succeed on the road, leading to a “Coors hangover” that consistently makes Rockies pitchers perform far worse on the road than their talent would suggest.

The Rockies have been able to produce a few innings-eating starters from their system, but Francis has the potential to be much more than that. Encouragingly, young Rockies starter Joe Kennedy, who like Francis is a flyball pitcher who throws hard for a lefty and sports a good changeup, ran up a 3.66 ERA last year, which was a tremendous performance. Maybe Francis should share his Gatorade.

In any event, Francis is my pick out of a thin crop of NL rookies that includes plenty of players who either lack a defined role, like the Astros’ Chris Burke and the Mets’ Victor Diaz, or aren’t really all that good, like the Brewers’ J.J. Hardy.

Over in the American League, there are a great many more rookies with the potential to make an impact, many of them on legitimate contenders. Later this year, the White Sox will probably call up Brendan McCarthy, who very nearly made a team with five veteran starters on the basis of an exceptional spring in which he demonstrated preternatural poise and exquisite control.

The Angels should bring up third baseman Dallas McPherson by the end of the month; he may pose a threat to the single-season strikeout record, but he’s also a fine bet to replace the production of the departed Troy Glaus. And as Mets fans are all too aware, the most exciting rookie in the game may be Tampa Bay’s diminutive lefthander Scott Kazmir, who is right now probably a better starter than the man for whom he was traded, Victor Zambrano.

The most hyped of all is probably Athletics rightfielder Nick Swisher, made famous two years ago in Michael Lewis’s “Moneyball.” I think he represents all the downsides of Oakland’s philosophy.

Drafted out of college and having taken three years to get to the majors, he’s already 25 – old for an impact rookie, and not likely to get much better than he already is. He’s a horrible hitter for average, and while average may be an overrated stat, it’s hard to contribute at an offensive position like right field when you hit .240.That’s not all, though. He doesn’t play defense, he doesn’t have speed, and he’s demonstrated little more than midrange power. His main attributes are his salary (low) and his batting eye, but he’s not going to draw 103 walks in the American League like he did in Triple-A last year.

The real deal is playing elsewhere in the A.L. West. The player most likely to have an impact on the pennant race is Seattle’s Jeremy Reed, whom the Mariners acquired in a bizarre deal from the occasionally brilliant and occasionally clueless White Sox.

Reed is best known for hitting .409 for 242 at-bats in Double-A in 2003, and he hit .397 in 58 at-bats in the American League last September. He’s a competent centerfielder with some skills on the base paths and an average walk rate, so despite not having much power at all, he’ll be a solid enough player if he hits .290. He also has an outside shot at being a .330 hitter as soon as this season.

That would make him a very valuable player, and in today’s game, a rare one. Reed is my pick for the AL Rookie of the Year. It may just be a hunch, but I don’t think he’ll be breaking the hearts of anyone except White Sox fans for a long time to come.