Smith, who was NFC Offensive Player of the Week just one month ago, is medically cleared after suffering a concussion Nov. 11 against the Rams, but he won’t be playing for the second Sunday in a row when the 49ers and Rams square off.
Coach Jim Harbaugh  has again named Kaepernick the starter this week.
“I feel like the only thing I did to lose my job was get a concussion,” Smith said.
Smith ranks fifth in the NFL with a passer rating of 104.1 and leads the league with a 70.0 completion percentage.
“You kind of state your case with your play and I felt like I’ve done that,” Smith said. “It’s tough. It stings the most just because I really felt there was something special going on here and you sacrifice and invest so much time. I felt like I was playing good football. I have no idea what’s going to happen from here. All I can do now is just prepare and get ready.”
Since replacing Smith, Kaepernick has completed 48-of-74 passes for 680 yards and three touchdowns with one interception, and he’s been sacked six times. He led the 49ers past the Saints and Bears.
Harbaugh says he’ll keep his mind open going forward about whether to use Kaepernick or Smith.
“Alex is a class act all the way,” Harbaugh said. “He’ll prepare as if he is the starter. And that’s what we would expect. And be ready to go in and play and contribute to this football team. We’ve got two quarterbacks that we feel great about as the starting quarterback. Anything’s a possibility. I would assume nothing or rule out anything.”