The Astros on Wednesday claimed infielder Ryan Jackson off waivers from the Cardinals, while infielder Jake Elmore, outfielder J.D. Martinez and right-hander John Ely were all removed from the club's 40-man roster.
Elmore was claimed off waivers by the White Sox, while Ely was released by the Astros and Martinez was outrighted to Triple-A Oklahoma City. With the quartet of roster moves, the Astros currently have 34 players on their 40-man roster.
Jackson joins the Astros after spending the majority of the 2013 season at Triple-A Memphis where he hit .278 with 19 doubles and 34 RBIs in 121 games. The 25-year-old primarily played shortstop for the Redbirds, though he also took reps at third base and second base. A fifth-round pick in the 2009 First-Year Player Draft, Jackson has played 20 games in the Majors over the past two seasons.
As for Elmore, the 26-year-old utilityman leaves the Astros after hitting .242 (29-for-120) with just two homers and six RBIs in 52 games this past season.
Martinez, meanwhile, will remain in the organization after hitting .250 with seven homers and 36 RBIs in 86 games with Houston this year. Originally selected by the Astros in the 20th round of the '09 Draft, Martinez has hit .251 with 24 home runs and 126 RBIs over the past three seasons with the Astros.
Lastly, Ely's release comes after the righty was limited to just one appearance this past season before undergoing Tommy John surgery on April 24.
Paul Casella is a reporter for MLB.com. Follow him on Twitter @paul_casella.