Originally, the timetable for recovery was two to three weeks. But general manager Ed Wade said Tuesday Matsui could need four weeks from the surgery date of March 17 to fully recover and return to the field.
That means Matsui may not make his Astros debut until April 15, when the Astros open a road series with the Phillies.
"He's supposed to be able to progress, they thought, after the second week," Wade said. "I'm still looking at it as a minimum of four weeks before we see him play. That's what I'm guessing. Nobody's told me that, but that's what I'm guessing.
"If you say three weeks [of recovery time] and the first week is basically consumed with next to nothing, it seems to me to get his skills back, if it's three weeks, that would be great."
Matsui rejoined the Astros in Kissimmee, Fla., on Sunday after spending nearly a week in Houston recovering from the procedure. He attended the Astros' game on Tuesday in Lakeland, Fla., where he played catch and stood at his position at second base during batting practice. He also spent time in the outfield, but he was largely inactive during the club's hour-long BP session.
Matsui will be examined by team doctors on Friday when the team returns to Houston. The long layoff may necessitate a Minor League rehab stint, but nothing has been decided on that front.
"I haven't talked with the manager about that so at this point I have no idea," Matsui said. "I have to get better first, I have to get going.
"I want to play in a game as soon as possible. That's a decision for the manager. I will try my best to be ready to play. After that, it's up to them. It's their decision to make."
In other injury news, J.R. Towles started Tuesday's game but manager Cecil Cooper is still waiting for his projected starting catcher to progress to 95 percent strength. Towles has been hampered by a strained hamstring for much of the spring.
"Waiting on a 95 percenter," Cooper said. "It's not even close. It would be nice to get him to 95. It's tough to do hit and runs with him not there yet. Hopefully, by the weekend, he'll be there."
Infielder Geoff Blum did not make the trip to Lakeland after he aggravated a left heel injury during the Astros' game in Jupiter on Monday.
"I'm hoping tomorrow he's OK so I can put him in there a little bit," Cooper said. "Maybe [at] first base, so I can get him a couple at-bats."
The Astros announced two other roster moves on Tuesday. They reassigned catcher Josh Johnson to Minor League camp, and they optioned right-hander Ryan Houston to Triple-A Round Rock.
The Astros have 32 players remaining in big league camp who are eligible to make the Opening Day roster.
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.