Pitcher Chad Reineke was optioned to Triple-A Round Rock to make room on the 25-man roster for Matsui.
Reineke had been recalled Tuesday in an effort to provide the Astros' bullpen with an extra arm in case of emergency. He did not pitch.
Matsui began the season on the disabled list after signing as a free agent with Houston during the offseason. When he returned, the Astros won 12 of their next 18 after starting the season 6-10.
