The old adage is that baseball is a kid’s sport played by men. This myth is further held in place by the players being nicknamed “the boys of summer.” In honor of the beginning of the dog days of summer and the “boys” that play the great American pastime, here are the top 10 fantasy baseball players under the age of 25.

10) Austin Jackson, Outfielder, Detroit Tigers (23 years old)
The 23-year-old that was sent to Detroit in the Curtis Granderson deal has made quite a name for himself in his rookie season in the Motor City. After being a highly-touted rookie, Jackson has produced in a big way during his rookie campaign. He’s batting .307 with a .355 OBP at the leadoff position, in addition to 16 stolen bases and 25 RBIs. Although he likely won’t win “Rookie of the Year,” he should make an impact in the AL Central for years to come.

9) Matt Wieters, Catcher, Baltimore Orioles (24)
Although he has played for absolutely dreadful teams during his first two years in the big show, Matt Wieters has slowly become one of the best young players in the game. On a team almost completely deficient in talent, Wieters batted .288 with 9 home runs and 43 RBIs in part-time duty last year. He’s defined sophomore slump in his second season, but he has all-world talent and if the Orioles can start to put quality players around Wieters, then it’s likely he’ll continue to get better and better.

8) Jason Heyward, Outfielders, Atlanta Braves (21)
In his rookie season, he has survived the non-stop hype and injuries and is still turning in an outstanding first season. His average is a bit on the low side at .261, but it should get higher as his career progresses if he .375 OBP is any indication. He has some power to go with his average and OBP to the tune of 11 home runs and 50 RBIs, even with the amount of time he missed. While it’s likely he’ll get the Rookie of the Year honors this season, he should get honored each of the next many seasons by going high on fantasy leagues’ draft boards.

7) Steven Strasburg, Starting Pitcher, Washington Nationals (22)

While Heyward has been hyped ever since he was in high school, the level of hype that 22-year-old Strasburg faced in his one season of minor league baseball was unmatched. And rightfully so. He’s got a full arsenal of pitches, the ability to get lots and lots of strikeouts and he ha six wins in limited time on the Nationals’ staff, which makes him an easy candidate for a top pitcher in any fantasy league.

6) Buster Posey, Catcher, San Francisco Giants (23)
Forget about his unorthodox name, this long-time touted catcher is finally up for the Giants and will be putting a dent in the Giants’ box scores and smiles on fantasy owners faces for a long time. In his short time in the big show, Posey is batting .342 with a .389 OBP, has hit 8 home runs with 39 RBIs, all in 61 games. And even though his average probably won’t stay that high for an entire season, it isn’t unreasonable to expect power numbers along with an average north of .300 and an .OBP above .350.

5) Andrew McCutchen, Outfielder, Pittsburgh Pirates (23)
Another young talent trapped on a losing team, McCutchen is quietly putting up great numbers in centerfield for the Pirates, even though he seemingly has new teammates each week. The 23-year-old has quickly made a splash in the centerfield-loaded NL Central, where in a little over one season since his debut, he has mashed 21 home runs, 87 RBIs, 44 stolen bases, along with a batting average of .281 and an OBP of .361. He is the kind of player that the Pirates–and just about any fantasy baseball owner–can build around.

4) Delmon Young, Outfielder, Minnesota Twins (24)
It took Young, the former No. 1 overall pick and little brother of former star Dmitri Young, a long time to make his mark. Better late than never. Although he barely qualifies for this list at 24, Young is having one of he best seasons of any outfielder in baseball. He’s carrying a .321 batting average and .352 OBP in the middle of June, to go with 14 home runs and 84 RBIs. Even though he wasn’t drafted early–or at all in many leagues–it’s better to be late than never to pick up on this rising star.

3) Justin Upton, Outfielder, Arizona Diamondbacks (22)
At the ripe age of 22, Justin Upton is wise beyond his years on the baseball diamond. While his older brother B.J. has struggled in Tampa Bay, Justin has put up ungodly numbers in three full seasons in Phoenix. In 2010, he’s batting .280 with a .365 OBP. As if that wasn’t enough, he has also hit 16 home runs, driven in 56 RBIs and stolen 13 bases. It’s scary to think that if he’s putting up these numbers at 22, what he’ll do in his prime.

2) Carlos Gonzalez, Outfielder, Colorado Rockies (24)

A key component of the Dan Haren and Matt Holliday trades, this “Car Go,” as he is nicknamed, is blockbuster trade cargo no more. After two partial seasons in the majors, Gonzalez is putting together a 2010 campaign that would make fantasy owners every drool. He’s batting .327, posting an OBP of .355, has hit 25 home runs, driven in 77 runs and stolen 18 bases. With numbers like that, he won’t be the mile-high secret much longer.

1) Evan Longoria, Third baseman, Tampa Bay Rays (24)
The poster-boy for the rebuilt Rays team has put up stellar numbers since joining the big club three years ago. Although he is one of the older members of this list at 24, it’s hard to ignore his numbers along with his age. In 2010, a down-year compared to his 2009 season, Longoria is batting .285 and is posting an OBP of .374. While he clubbed 33 home runs last season, he only has 15 this year, but has made up for that with his 70 RBIs and 15 stolen bases. Simply stated, he’s the best player in the game under 25 years of age.