The team waived the veteran cornerback to clear room on the active roster for fellow defensive back Eric Wright.
Asomugha had struggled since taking control of the third cornerback role in August and found himself inactive on game days with players like Tramaine Brock and undrafted rookie Darryl Morris taking the field instead.
The return of Wright, who's been practicing since Oct. 15 after suffering an undisclosed injury, cleared the way for the 49ers to part ways with 32-year-old Asomugha.
Once thought to be one of the top corners in the league, Asomugha's play has fallen off since he signed a big free-agent deal with the Philadelphia Eagles prior to the 2011 season.
In another Monday roster move, San Francisco activated wide receiver Mario Manningham, who has been out since suffering a season-ending knee surgery last year. Manningham will help shore up the 49ers' recieving corps until Michael Crabtree is able to return from injury later this season.
San Francisco will host the Carolina Panthers in Week 10.
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