Linebacker Jeff Ulbrich and safety Michael Lewis sat out practice after experiencing recent concussions. Ulbrich's situation appears to be the most serious. Both players were scheduled to undergo further tests Wednesday.
Singletary said Lewis' concussion symptoms cleared quickly on Sunday. He has experienced three concussions since mid-August, so the 49ers are taking no chances, Singletary said.
"(Lewis) was ready to go," Singletary said. "He could've played. Twenty years ago he would've been smelling smelling salts and been back in the game. But that wasn't the case."
Smith took his first snaps with the 49ers' offense since training camp, as starting quarterback Shaun Hill was held out of practice due to soreness, Singletary said.