BP: Baseball's best young player

The Diamondbacks enter the 2010 season with a slew of question marks about their roster. Will Brandon Webb successfully return from shoulder surgery? Can Edwin Jackson make fans forget the questionable trade of Max Scherzer? Is this the year Stephen Drew finally establishes himself as a legit threat? And will Chris Young stop hitting like he’s the other Chris Young? With so much up in the air, it’s easy to forget the Snakes boast superstar-in-the-making Justin Upton -- and the numbers show he might be the best young talent in the game. We've spent a lot of time this spring talking about what Jason Heyward might do; it's easy to forget that Upton is already doing it.

Upton's 2009 campaign was so good that there are few to which you can compare it. After all, how many 21-year-olds are capable of producing a .366 OBP/.532 SLG in the major leagues with 20-plus dingers and 20-plus steals? To find out, we sifted through about the past half-century of players, looking for those who met the following criteria in a season:

• 21 or younger
• 450 plate appearances or more
• .350 OBP or higher
• .500 SLG or higher
• 20 home runs or more
• 10 stolen bases or more

And only seven players qualified:

In A Class Of Their Own

Here are the players who -- at 21 years old or younger -- had at least 450 plate appearances, a .350 OBP, a .500 SLG, 20 home runs and 10 stolen bases.

Upton placed himself in extremely limited company last season, and his peers don’t need any introduction. Even the lesser-known names above -- like Vada Pinson and Cesar Cedeno -- carved out solid careers, with the former racking up more than 2,700 hits, 256 homers and 305 steals, and the latter bopping 199 dingers to go with 550 steals.

But here's another way to put Upton's 2009 season in perspective: How many players his age or younger have produced a .230 Isolated Power? Fourteen.

Players who have achieved the feat include Eddie Matthews, Mel Ott, Frank Robinson, Albert Pujols, Alex Rodriguez, Jimmie Foxx, Ted Williams and Joe DiMaggio, among others.

PECOTA forecasts Upton to hit a nice .282 BA/.357 OBP/.501 SLG in his third full season -- a bit of a regression from his fantastic 2009 campaign. But when a slash line like that seems low to the naked eye, you know you have something special. Although Upton hasn’t forced his way into the spotlight by hitting 40 home runs or stealing 50 bases, it's only a matter of time before he does.

Eric Seidman is an author of Baseball Prospectus.