The 49ers made a pair of roster moves on Tuesday, promoting cornerback Darryl Morris from the practice squad to the 53-man roster, and signing linebacker D'Aundre Reed to the practice squad. The 49ers placed Aldon Smith on the Reserve/NFI list on Monday, which opened up a roster spot. They worked out Reed this week.
Although I had thought we would see the team sign an outside linebacker to the 53-man roster, the decision to promote Morris likely has something to do with Nnamdi Asomugha's knee injury. Nnamdi suffered the injury late against the Colts, and sat out yesterday's practice. Coach Harbaugh indicated Nnamdi would get an MRI. We don't know the results of the MRI, but it would seem likely that Nnamdi will not play this Thursday against the Rams.
If Nnamdi does indeed sit out, Tramaine Brock is likely to move up into the nickel corner rotation. Perrish Cox could see some work as well, but he usually operates as Carlos Rogers' backup as the slot corner in the nickel. Cox comes on in the dime, but that seems more conducive to his slot corner role.