The 49ers signed cornerback Donald Strickland on Tuesday, adding another veteran defender to one of the NFL's worst defenses. Strickland, a San Francisco native, started 12 games during 2 1/2 seasons with the Colts, who waived him last year. He also played three games for the Eagles in 2005. The 49ers waived cornerback B.J. Tucker to make room for Strickland, but the club hopes to sign Tucker to the practice squad Wednesday.