Head athletic trainer Dave Labossiere left behind a rehab program for Matsui and will keep in contact with the second baseman while the team is out of town. The Astros are hopeful Matsui will be ready to come off the disabled list when he's eligible on Aug. 28, which falls in the middle of the next homestand with the Reds and Cardinals.
"Being this late in the year, hopefully, when we get back, he can do baseball stuff and get close there," manager Cecil Cooper said.
For now, baseball-related activities are off-limits for Matsui, who is on the DL for the third time this year. His current problem involves an irritated disk in his lower back, an issue that has plagued him at times during his career.
Carlos Lee also didn't make the trip to Milwaukee, and because he's out for the year, it's possible he won't travel with the team for the rest of the season.
Cooper, however, hopes Lee will be around when the team plays at home.
"He said he'd come out a few days during the next homestand to help with the hitting situation, talk to the young guys," Cooper said. "Just help us out a little bit."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.