CB Shawntae Spencer will have season-ending surgery today on his torn ACL in his left knee. The loss of Spencer will have a big impact on the secondary. Spencer was third on the depth chart and had played well in the first two games before being hurt at the end of the Seahawks game. His backups include Donald Strickland who has missed the last two games with a sprained knee and Tarell Brown who made his first appearance of the season last week against the Lions. Strickland does not know if he will play this weekend against the Saints which means Brown should be at the third spot on the depth chart. Brown played well last week against the Lions powerful receivers whom he helped shut down along with the rest of the secondary. However it is risky to have Brown, who has played in only nine games as a second year player, to be the number three man in the secondary. But the 49ers play the Saints this weekend minus two receiving threats as Marques Colston and Jeremy Shockey are out with injuries. What is more troublesome are the receivers the secondary will face after this weekend’s game (Randy Moss, Wes Welker, Plaxico Burress, DeSean Jackson) . Brown needs to show in the game against the Saints he can be the third man in the secondary and shut down receivers when tasked with the job.