Kuzul

Castro, who turned 20 on March 24, had a fantastic run in the Arizona Fall League that brought him national attention. Now his presence in Spring Training has some people in the Chicago media asking Ryan Theriot how soon he’ll be playing second base.

As the Tribune’s Paul Sullivan wrote, “Over the last eight months, Castro has gone from unheralded to untouchable.”

Many prospect rating groups are now releasing their baseball prospect lists, and Castro is prominently featured. On every list, Castro is now the Cubs’ top prospect, and he has jumped into the top 20 on most national rankings.

Cubs VP of player personnel Oneri Fleita recently told MLB.com , “He is the type of player I would pay to watch play.”

Baseball America , the largest and most respected minor league baseball information source, ranked Castro the 16th-best prospect in all of baseball. ESPN ‘s Keith Law ranked him 12th overall, and had some wonderful things to say about the young man. MLB.com ranked Castro the lowest of the three, at 22nd overall.

“Castro is one of the most exciting position player prospects in the minors as a quick-twitch player with an electric bat and a hose for an arm at shortstop,” said Law. “As a shortstop, he’s quick on his feet with good range in both ways, especially to the hole, but it is his arm that really stands out…He’s going to be an impact bat in the middle of the diamond.”

In this post-Moneyball world where on-base percentage is king, Castro’s tiny walk total from last year isn’t very popular. His strike out rate, though, indicates that he puts the ball in play. Castro drew only 29 walks, but struck out just 53 times in 469 total at-bats last year.

MLB.com said, “[Castro] could be ready to take over in Chicago sooner rather than later, with all the ingredients to be an elite, All-Star caliber shortstop.”

Castro has shown some speed on the bases as well. In 127 games in 2009, he stole 28 bases in 39 attempts. He has not yet shown much power, but there aren’t many 19-year-old shortstops that do.

So it sounds like Cubs fans have the next Derek Jeter headed to Wrigley on his golden chariot in time for Opening Day, right?

Not so fast…

FanGraphs did some interesting homework with help from BaseballReference  on young players breaking into the majors and came up with some intriguing information.

From 1954 to 2009, only 12 middle infielders crossed the rookie threshold as a 20-year-old. That group, which includes familiar names like Roberto Alomar, Jose Reyes, Garry Templeton, and Elvis Andrus, batted only .261 in their rookie seasons. Indeed, all of the youngsters struggled in their matriculations.

It won’t be long until we see the Starlin-O-Meter in the bleachers. He’s the best home-grown shortstop since Shawon Dunston, and now that he’s in Chicago the world will be watching.