Crim was drafted in the 21st round of the 2009 draft after attending The Citadel, and was the 2009 Appalachian League player of the year for the Danville championship team. It was his finest season as a pro, going 10-2 with a 3.18 ERA, 48 strikeouts, and 10 walks in 68 innings. In 2010 for Myrtle Beach, Crim went 7-11 with a 4.87 ERA, 86 strikeouts, 59 walks, and 15 homers allowed in 149 2/3 innings. This past season, Crim was used mainly out of the bullpen, starting just 11 games between Lynchburg and Mississippi. Combined at the two levels, he had a 5.83 ERA with 26 walks and 57 strikeouts in 83 1/3 innings. Crim is 24, and when you have peripherals that bad in the low minors at that age, there's not much hope for a turnaround.
Richardson is a former fifth round pick of the Boston Red Sox in the 2006 draft, and was acquired by the Braves in the middle of 2011 from the Marlins organization. During his tenure in Gwinnett, he had a 6.00 ERA in 30 innings, walking 22 and striking out 29. He was roster filler, and nothing more.
Cabrera was drafted in the 14th round of the 2005 draft by the Braves, and was a postseason All-Star in 2006 with Danville and 2008 with Myrtle Beach, and a midseason All-Star with Mississippi in 2010. 2011 was the worst year of his career, with a slash line at Gwinnett and Mississippi of .256/.303/.352. His best two seasons came in 2008, where he had a .289/.344/.469 line in 125 games for Myrtle Beach and Mississippi, and 2010, where he had a .298/.359/.439 line in 107 games for Missisippi and Gwinnett. As a 25 year old who struggled in a pair of brief tenures with Gwinnett (8/50, 13 strikeouts), it seemed like there wasn't much of a place for him in the upper levels of the organization. One strong suit about Cabrera is his inability to strikeout, as the highest strikeout total he posted in his career was just 59, over a 511 at bat season.
EDIT: Marcus Lemon also released. He was acquired from the Rangers last season, and had a .254/.303/.333 line for Lynchburg and Mississppi over 108 games. He was a former fourth round pick of the Rangers (who got a seven figure signing bonus), and has now posted sub-.700 OPSes for three years running.