Marc Hulet did a nice job of ranking the San Francisco Giants farm system over at FanGraphs on Tuesday. What stood out about his rankings is easy to see: of the Giants’ top seven prospects, six of them are pitchers.

The Giants have rebuilt their farm system around pitching over the last two drafts. They selected top prospect Kyle Crick in the supplemental first round of the 2011 draft, No. 2 prospect Clayton Blackburn in the 16th round of the same draft and No. 3 prospect Chris Stratton with their first-round pick last season.

Crick, Blackburn and Stratton are reinforcements for a farm system that lost top pitching prospect Zack Wheeler—the team’s first-round pick in 2009—in the trade for Carlos Beltran midway through the 2011 season.

The Giants farm system also has produced the core of their outstanding big league rotation in first-round picks Matt Cain (2002), Tim Lincecum (2006) and Madison Bumgarner (2007). Ryan Vogelsong returned to the organization prior to 2011 as a minor league free agent after being originally drafted by the team back in 1998, and he has since emerged as a front-line starter for the Giants.

The rest of the top 15 is heavy on position players, but I think Hulet made two significant omissions on the pitching side of the prospect list. He ranked Crick, Blackburn and Stratton as the Giants’ top three pitching prospects, followed by Heath Hembree, Mike Kickham, Josh Osich, Edwin Escobar and Adalberto Meija.

However, he left off 2012 second-round pick Martin Agosta and the Giants minor league pitcher of the year last season, Chris Heston. 

Agosta struck out 19 of the 50 batters that he faced in rookie ball last season, and Heston put up a 2.24 ERA in 148.2 innings at Double-A last year. Heston has had good results throughout his minor league career, but he lacks the fastball velocity necessary to be considered a future top-of-the-rotation starter. He projects as more of a back-end arm who will throw strikes and get plenty of ground balls.

I would have left shortstop Ehire Adrianza and outfielder Francisco Peguero off of the list of top prospects in favor of Agosta and Heston. Adrianza is an excellent defender, but he’ll never hit enough to play consistently in the big leagues. Peguero will turn 25 next season, which is a bit old for a prospect. He has tools, but his plate discipline is so bad that it’s hard to imagine him turning into more than a fifth outfielder.

The Giants are light on positional prospects, with center fielder Gary Brown—a first-round pick in 2010—and shortstop Joe Panik—a first round pick in 2011—topping a list that also includes Adrianza, Peguero, catcher Andrew Susac, right fielder Roger Kieschnick and third baseman Adam Duvall.

Brown appeared on the fast track to the big leagues after an excellent 2011 season at High-A San Jose, but he hit just .279/.347/.385 at Double-A last year. The Giants locked up incumbent center fielder Angel Pagan with a four-year deal this offseason, so Brown’s path to the big leagues with the Giants is blocked unless the team decides to slide Pagan to left field in the future.

Brown will need to rebuild his stock as a prospect either by repeating Double-A next season or in Triple-A if the Giants decide to promote him. Right now there are questions as to whether he projects as a fourth outfielder or as an everyday regular in center field.

Panik hit .297/.368/.402 with 58 walks against just 54 strikeouts at High-A San Jose last season, but then he hit only .205 in 20 games against stiffer competition in the Arizona Fall League. The jump to Double-A next season will help determine if his future in the big leagues is as an everyday starter or as a utility man.

This will be a key season for the Giants in deciding the future of their rotation. Cain and Bumgarner are locked up through 2017, but Lincecum, Vogelsong and Barry Zito can all become free agents after 2013 if the Giants do not pick up the club options on Vogelsong and Zito.

Heston and Kickham (3.05 ERA) threw well at Double-A this year, so they are much closer to the big leagues than Crick, Blackburn, Stratton, Escobar and Agosta, who all could be slotted together in the same rotation at San Jose next season.

It will be interesting to see how Kickham and Heston adjust to pitching in the hitter-friendly Pacific Coast League next season and how quickly the Giants’ younger top pitching prospects climb the minor league ladder. Stratton could be a fast mover because of his collegiate experience pitching in the SEC at Mississippi State.

The Giants’ big-league rotation is full for now, but it won’t be for much longer as three of their starters approach free agency. The Giants have shifted their focus in the draft back to pitching, and reinforcements are on the way. 

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