Astros general manager Jeff Luhnow announced Friday that Houston has placed right-hander Kyle Weiland on the 15-day disabled list -- retroactive to April 25 -- due to right shoulder bursitis.
Also, infielder Marwin Gonzalez was placed on the Paternity List.
The 25-year-old Weiland has posted a 0-3 record with a 6.62 ERA over 17 2/3 innings in three starts for Houston so far this season.
Weiland was acquired by Houston, along with shortstop Jed Lowrie, from the Boston Red Sox last December in exchange for Mark Melancon.
He compiled a 0-3 record with a 7.66 ERA and 13 strikeouts over 24 2/3 innings in seven games (five starts) for Boston last season.
Weiland stepped up this spring by going 2-1 with a 2.86 ERA in six games (four starts) to earn a spot in the Astros' starting rotation.
Gonzalez can be on the Paternity List for up to three days.
The young infielder is hitting .231 with an RBI, three doubles and six runs scored over 39 at-bats in 16 games for Houston this season.
Gonzalez, 23, was acquired by the Astros from Boston last December in exchange for right-hander Marco Duarte and cash.
He had been selected by the Red Sox in the first round of the Major League phase of the Rule 5 Draft off the Cubs' Triple-A Iowa roster.
Gonzalez was then dealt to Houston afterward.
His Rule 5 status does apply, meaning he must remain on the Astros' roster throughout the 2012 season or be offered back to the Cubs.
Abad, 26, made the Opening Day roster and compiled a 6.75 ERA in two appearances before being optioned to Triple-A on April 9.
The left-handed reliever struck out 12 while walking two over 7 1/3 shutout innings in five relief appearances for Oklahoma City.
Bixler, 29, went 1-for-6 with two runs scored over seven plate appearances for Houston prior to being optioned to Triple-A on April 12.
He hit .429 (21-for-49) for Oklahoma City.