Jeff Bagwell went on the disabled list Tuesday for the first time in seven seasons, an ominous setback in his battle with a degenerative shoulder condition. Bagwell, who turns 37 this month, missed just 12 games over the past three seasons despite arthritis in his right shoulder. But playing has become too painful, the Houston Astros' first baseman said. ``My arm has shut down a little bit,'' he said. ``I just don't have the arm strength to get the ball to the infielders during warmups or get the bat head to the ball.'' The move was made retroactive to May 4, meaning Bagwell will be eligible to come off the disabled list May 19. The four-time All-Star said he hopes to rejoin the lineup then, but the Astros aren't counting on it. ``We'll see if a period of shutdown will help,'' general manager Tim Purpura said. ``There's no guarantee that this is going to make a significant difference.'' Taking Bagwell's roster spot was infielder Todd Self, called up from Triple-A Round Rock.