HOUSTON -- Kazuo Matsui's debut with the Astros won't happen until next Friday at the earliest, Houston general manager Ed Wade said Sunday morning.

Matsui, who has been on the disabled list since before the season started after undergoing a medical procedure to repair an anal fissure, saw his scheduled four-game rehab assignment end after two games when his back stiffened before Friday's game.

"[Matsui] was examined by Dr. [Tom] Mehlhoff, and he's been cleared to resume his workouts," Wade said. "The plan is he'll work out [at Minute Maid Park on Monday] morning and then fly to Oklahoma City for a three-game rehab assignment [with Triple-A Round Rock] on Tuesday, Wednesday and Thursday. If all goes well, hopefully he'll be reinstated next Friday."

The Astros initially had hoped to have the second baseman back in time for the three-game series at Philadelphia beginning Tuesday.

Matsui batted .417 with one home run and six RBIs for the Rockies in last October's National League Division Series against the Phillies. His grand slam off Kyle Lohse in the fourth inning of Game 2 broke the game open for Colorado, which went on to reach the World Series.

Wade said the back stiffness was related to the 32-year-old Matsui's inactivity in recent weeks.

"This is basically Spring Training for him," the GM said.

Matsui, who signed a three-year, $16.5 million free-agent contract with Houston during the offseason, has been sidelined since March 21.

Veteran Mark Loretta has received the bulk of the playing time at second base during Matsui's absence.