The San Francisco 49ers promoted rookie cornerback Darryl Morris from the practice squad to the 53-man roster. It is an indication No. 3 cornerback Nnamdi Asomugha may not be ready to play Thursday at St Louis.Asomugha suffered a leg injury in the loss to the Colts on Sunday.Morris is an undrafted free agent from Texas State. He takes the roster spot that was created when the 49ers put star pass-rusher Aldon Smith on the reserve/non-football illness list.