Signing Day: 5 players drafted 1st out of high school

National Signing Day is finally here, and that means we're just hours away from finding out where some of the most talented high school football players in America will groom their skills with the hopes of being drafted to the NFL one day.

The NFL has a clause stating that in order to be drafted, a player must have been out of high school for a minimum of three years. No such rule exists in the realm of professional baseball, however, and every year several players ink big-league deals right out of high school.

Here are five current players that were selected first overall in their respective draft classes without ever playing collegiate baseball:

Alex Rodriguez

Westminster Christian School (Miami, Fla.)
Draft year: 1993
MLB team: Seattle Mariners

A-Rod signed a letter of intent to play baseball for the University of Miami, but he elected to turn down the offer after being selected first overall by the Mariners at the age of 17. Also a promising high school quarterback, A-Rod quickly proved he made the right decision by making his major-league debut one year later in July, 1994.

Josh Hamilton

Athens Drive (Raleigh, N.C.)
Draft year: 1999
MLB team: Tampa Bay Devil Rays

Hamilton already boasted a big-league frame during his senior year, standing 6-foot-4 while weighing in at 200 pounds. Both a pitcher and outfielder during his high school playing days, Hamilton's fastball topped out at an incredible 96 miles per hour, but his .529 batting average in his senior year was what really caught the attention of scouts. Hamilton would go on to sign a then-record $3.96-million signing bonus with the Rays, who coveted him more than right-hander Josh Beckett and southpaw Barry Zito.

Joe Mauer

Cretin-Derham Hall (St. Paul, Minn)
Draft year: 2001
MLB team: Minnesota Twins

Mauer was named All-State in three sports - baseball, football, and basketball - during his senior year at Cretin-Derham, which is the same school Hall of Famer and current Twins manager Paul Molitor hails from. Mauer earned National Player of the Year honors in 2000 for his accolades as a quarterback, and even signed a letter of intent with Florida State University to play football. However, after many successful stints as a catcher for USA's national junior baseball team, Mauer opted to enter the MLB draft and was delightfully selected by his hometown Twins.

Adrian Gonzalez

Eastlake (Chula Vista, Calif.)
Draft year: 2000
MLB team: Florida Marlins

Gonzalez, who grew up playing baseball in Mexico before his family moved to Bonita, Calif., entered his senior season as a projected second-round pick, but his draft stock quickly rose after he hit .645 with 13 homers and 34 RBIs in 76 at-bats. Like Rodriguez, the University of Miami offered Gonzalez a scholarship, but after working out 10 times privately for the Marlins, A-Gon solidified himself as a worthy top pick in the minds of team executives.

Justin Upton

Great Bridge (Chesapeake, Va.)
Draft year: 2005
MLB team: Arizona Diamondbacks

Growing up in the shadow of his older brother, Melvin - a second overall selection of the Devil Rays in 2002 - Justin displayed an uncanny ability to hit home runs from an early age. After leading Great Bridge to its first state title as a sophomore, Upton gained the attention of Diamondbacks scout Greg Lonigro, who lobbied for Arizona to use its No. 1 pick on the youngster. It was a tough decision for the Diamondbacks considering the star-studded draft class in 2005 that also included now-MLB stars Alex Gordon, Ryan Zimmerman, Ryan Braun, Troy Tulowitzki, Andrew McCutchen, Jacoby Ellsbury, and Jay Bruce.