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Speedy Dee Gordon stole 24 bases in 56 games.
Jesus Guzman, 1B, San Diego
Guzman had an impressive season with a triple slash line of .312/.369/.478 to go with five homers and nine steals, but the reason he isn't included is because he only played in 76 games. If he put up similar numbers over the course of a full season, he'd rank very high on this list.
Darwin Barney, 2B, Chicago Cubs
Barney is the perfect example of why you can not judge a rookie by a half season, as he played above his head in the first half while hitting .306. He fell back to earth in the second half, hitting just .238 the rest of the way. Barney is more of a utility guy than an everyday player, but still deserves mention for a solid rookie year.
Dee Gordon, SS, Los Angeles Dodgers
The son of former major league reliever Tom Gordon, Dee is already one of the most exciting players in the game. Although he lacks any real power, he hit .304 and stole 24 bases in only 56 games. Like Guzman, Gordon missed the list because he didn't see enough time but would have ranked very high if he put up the same numbers over a full season.
Alex Presley, OF, Pittsburgh
Presley doesn't fit the top prospect bill as he is only 5'9" and already 25 years old heading into the season, but he hit minor league pitching well enough that the Pirates had to promote him. In his 52 games he was more successful than expected with his triple slash line reading .298/.339/.465 with four homers, 20 runs batted in and nine steals.
He just didn't see enough time to earn a spot in the top 10 because of his midseason promotion as well as missing time with injury. It will be interesting to follow Presley in 2012 to see if he can keep hitting at this pace.
Mike Minor, SP, Atlanta
Like some of the others above, Minor missed the top 10 based on the fact that he only played about half a season. Still in his 15 starts he went 5-3 with a 4.14 ERA and pitched very well down the stretch with his Braves in the middle of a pennant race.
Joshua Collmenter, SP, Arizona
Collmenter pitched in 31 games on the year, including 24 starts and posted a 10-10 record with a 3.38 ERA and 1.07 WHIP. The reason he just missed out on the final spot in the top 10 is because he went 3-1 with a 1.49 ERA through May, but just 7-9 with a 3.97 ERA the rest of the way.
Kenley Jansen, RP, Los Angeles Dodgers
Through May, the 23-year-old converted catcher had a 6.42 ERA in 20 appearances, but rebounded to give up only two more earned runs in his next 31 appearances. The only thing that could slow Jansen after May was a heart issue that cost him a couple weeks. After finishing 2-1 with a 2.85 ERA and 1.04 WHIP to go with 96 strikeouts in 53.2 innings, Jansen could end up stealing the closer's job away from teammate and fellow rookie Javy Guerra next season.
Aroldis Chapman, RP, Cincinnati
Like Jansen, the Cuban Missile struggled early with a 6.92 ERA in 13 appearances through May. After being demoted, Chapman responded well and pitched to a 2.43 ERA in his final 38 appearances. Overall he went 4-1 with a 3.60 ERA and 1.30 WHIP while striking out 71 in 50 innings.
Also like Jansen, Chapman may take over the closer role for his team next year depending on if the Reds bring back veteran Francisco Cordero.
Due to injuries promising young pitchers Rubba De LaRosa (Tommy John surgery) of the Dodgers and Juan Nicasio (broken neck) of the Rockies missed out on making this list, but were both having success before they were hurt.