Brown is recovering from a shoulder injury sustained during a practice session last week.
"He looked better," Shanahan said of Brown. "He got more reps today than he has throughout the whole week. By no means is he for sure though. I think it will be very similar to last week."
Colbert is attempting to return from a broken thumb suffered on November 12 against the New York Giants. Witherspoon injured his ankle on Wednesday while trying to go for the football during practice, according to Shanahan.
The good news is that quarterback C.J. Beathard (knee, hip) appears to be healthy enough to suit up on Sunday and back up newly named starter Jimmy Garoppolo. Beathard was injured during the closing moments of Sunday's loss to the Seattle Seahawks.
"He moved around well (in practice), plan on going in as the number two," Shanahan said of Beathard.
Below are the official injury reports for the 49ers and Bears. Also included are Friday's practice participation reports, which were provided by the 49ers Communications team.
San Francisco 49ers
Questionable
T Trent Brown (shoulder), S Adrian Colbert (thumb), CB Ahkello Witherspoon (ankle)
Chicago Bears
Out
LB Isaiah Irving (knee)
Doubtful
S Adrian Amos (hamstring)
Questionable
S Deon Bush (ankle), CB Bryce Callahan (knee), S DeAndre Houston-Carson (ankle), CB Cre'von LeBlanc (illness), G Josh Sitton (concussion)
San Francisco 49ers Friday Practice
Limited Participation in Practice
T Trent Brown (shoulder), S Adrian Colbert (thumb), CB Ahkello Witherspoon (ankle)
Full Participation in Practice
QB C.J. Beathard (knee, hip), DE Elvis Dumervil (not injury related), TE George Kittle (ankle), DT Earl Mitchell (not injury related), S Eric Reid (knee), T Joe Staley (not injury related), DE Solomon Thomas (knee)
Chicago Bears Friday Practice
Did Not Participate In Practice
S Adrian Amos (hamstring), S Deon Bush (ankle), S DeAndre Houston-Carson (ankle), LB Isaiah Irving (knee), CB Cre'von LeBlanc (illness)
Limited Participation in Practice
CB Bryce Callahan (knee), G Josh Sitton (concussion)
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