Atlanta acquired Aybar this past offseason in the trade that sent Andrelton Simmons to the Los Angeles Angels. A career .276 hitter through his first 10 seasons, Aybar is batting .182 with a .225 on-base percentage and a .209 slugging percentage in 44 games this year.
The 32-year-old former All-Star's season took an odd turn shortly before his injury, when he missed a game in Pittsburgh on May 19 because a chicken bone was lodged in his throat.
In seven rehab games with Gwinnett, Aybar batted .172 (5-for-29) and stole two bases.
Castro appeared at shortstop, second base and third base in 42 games this season. He was hitting .182 and had recorded only two hits in his past 27 at-bats.
Pat James is a reporter for MLB.com based in Atlanta. Follow him on Twitter @patjames24. This story was not subject to the approval of Major League Baseball or its clubs.