All Levels: MLB / AAA / AA / A+ / A
| Major Leagues | |||||||
| Rk. | Player | Pos | Age | DOB | Org | TBF/PA* | xFIP/PrOPS |
| 1 | Clayton Kershaw | SP | 20.5 | 3/19/1988 | LAD | 470 | 4.09 |
| 2 | Justin Upton | RF | 21.1 | 8/25/1987 | ARI | 578 | .819 |
| 3 | Jay Bruce | RF | 21.5 | 4/3/1987 | CIN | 453 | .833 |
| 4 | Ryan Tucker | SP | 21.8 | 12/6/1986 | FLA | 178 | 5.62 |
| 5 | Chris Volstad | SP | 22.0 | 9/23/1986 | FLA | 365 | 4.66 |
| 6 | Pablo Sandoval | 1B | 22.1 | 8/11/1986 | SF | 155 | .778 |
| 7 | Phil Hughes | SP | 22.2 | 6/24/1986 | NYY | 463 | 5.14 |
| 8 | Collin Balester | SP | 22.3 | 6/6/1986 | WAS | 358 | 5.18 |
| 9 | Homer Bailey | SP | 22.4 | 5/3/1986 | CIN | 385 | 5.34 |
| 10 | Billy Butler | 1B |
22.4 | 4/18/1986 | KC | 843 | .740 |
| 11 | Felix Hernandez | SP | 22.4 | 4/8/1986 | SEA | 2812 | 3.89 |
| 12 | Chris Davis | 1B | 22.5 | 3/17/1986 | TEX | 318 | .857 |
| 13 | Johnny Cueto | SP | 22.6 | 2/15/1986 | CIN | 769 | 4.62 |
| 14 | Nick Evans | LF | 22.6 | 1/30/1986 | NYM | 121 | .722 |
| 15 | Jair Jurrjens | SP | 22.6 | 1/29/1986 | ATL | 935 | 4.02 |
| 16 | Sean Gallagher | SP | 22.7 | 12/30/1985 | OAK | 596 | 4.94 |
| 17 | Carlos Gomez | CF | 22.8 | 12/4/1985 | MIN | 755 | .670 |
| 18 | Asdrubal Cabrera | 2B | 22.8 | 11/13/1985 | CLE | 606 | .746 |
| 19 | Carlos Gonzalez | CF | 22.9 | 10/17/1985 | OAK | 317 | .618 |
| 20 | Evan Longoria | 3B | 22.9 | 10/7/1985 | TB | 510 | .877 |
| 21 | Joba Chamberlain | SP | 23.0 | 9/23/1985 | NYY | 508 | 3.21 |
| 22 | Gio Gonzalez | SP | 23.0 | 9/19/1985 | OAK | 163 | 5.21 |
| 23 | Delmon Young | LF | 23.0 | 9/14/1985 | MIN | 1442 | .701 |
| 24 | Ryan Feierabend | SP | 23.1 | 8/22/1985 | SEA | 492 | 5.03 |
| 25 | Blake DeWitt | 3B | 23.1 | 8/20/1985 | LAD | 429 | .775 |
| 26 | Daric Barton | 1B | 23.1 | 8/16/1985 | OAK | 612 | .748 |
| 27 | Matt Harrison | SP | 23.1 | 8/16/1985 | TEX | 372 | 5.12 |
| 28 | Adam Jones | CF | 23.1 | 8/1/1985 | BAL | 659 | .674 |
| 29 | Greg Reynolds | SP | 23.2 | 7/3/1985 | COL | 294 | 5.74 |
| 30 | Chris Perez | RP | 23.2 | 7/1/1985 | STL | 177 | 4.53 |
| * TBF/PA is the sum of 2005, 2006, 2007, and 2008 | |||||||
| ** Minimum of 30.0 IP or 100 PA | |||||||
| ***xFIP and PrOPS are 2008 statistics from The Hardball Times | |||||||
Led by 20-year-old Clayton Kershaw, 20 big leaguers finished the 2008 regular season under the age of 23. And only a hanfdul of those youngesters already have a significant amount of big league experience: Felix Hernandez (2,812 TBF), Jair Jurrjens (935 TBF), Billy Butler (843 PA), Johnny Cueto (769 TBF), and Carlos Gomez (755 PA).
Expectedly, due to their lack of big league experience, the bulk of the players on this list didn't perform well in 2008. Hernandez, Jurrjens, Evan Longoria, and Joba Chamberlain are the only four who have really stood out in the big leagues over 500+ TBF/PA.
Two teams have three or more players on this list: the Oakland A's (Sean Gallagher, Carlos Gonzalez, Gio Gonzalez, and Daric Barton) and the Cincinnati Reds (Jay Bruce, Homer Bailey, and Johnny Cueto). Eleven teams don't have any players on the list: the Angels, Astros, Blue Jays, Brewers, Cubs, Padres, Phillies, Pirates, Red Sox, Tigers, and White Sox.
Sean Halloran can be reached via spiritual channeling during lunar eclipses. Adam Foster can be reached at adamf@projectprospect.com.