2010: Bryce Harper, OF, Nationals
It is hard to imagine a more hyped prospect than Harper -- unless it's the No. 1 overall pick from 2009, Stephen Strasburg. Harper graduated high school early and went to junior college for a year so that he would be eligible for the 2010 Draft. After spending one full season in the Nats' Minor League system, Harper made his Major League debut in 2012 and won the National League Rookie of the Year Award.
2011: Gerrit Cole, RHP, Pirates
An accomplished pitcher at UCLA, Cole spent 2012 working his way up the ladder in the Pirates' system and was promoted to the big leagues during the '13 season. He has quickly become the ace of the staff on a team that has made the postseason each of the past two years.
2012: Carlos Correa, SS, Astros
The rebuilding Astros selected the high school shortstop knowing that it would take him a little longer to reach the big leagues. Correa, though, is moving quickly. He began 2015 at Double-A Corpus Christi, but after posting a 1.185 on-base plus slugging mark, he was promoted to Triple-A Fresno. Correa's highly anticipated callup to Houston should happen sometime this season.
2013: Mark Appel, RHP, Astros
Originally selected by the Pirates in 2012, Appel did not sign and returned for his senior year at Stanford. Expectations are always high for a No. 1 pick, but they've been even more so for Appel, given that the Cubs selected Kris Bryant with the No. 2 overall pick. Appel's numbers have not been good so far this year in Double-A, but the Astros still believe that he will eventually be a top-of-the-rotation starter.
2014: Brady Aiken, LHP, Astros
The high school left-hander out of San Diego became the biggest story out of last year's Draft for all the wrong reasons. The Astros reportedly did not like what they saw on a MRI taken of his elbow during a routine physical, and that started a contentious negotiation that ended in Aiken not signing. Aiken eventually underwent Tommy John surgery and will re-enter the Draft this year, while Houston got the No. 2 overall pick as compensation.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.