The Bears on Wednesday officially ruled quarterback Justin Fields (ribs), defensive tackle Akiem Hicks (ankle) and running back Damien Williams (calf) out of Thursday's game in Detroit.
All three players would not have been able to practice this week had the Bears conducted a regular workout instead of just walk-throughs.
Fields exited last Sunday's 16-13 loss to the Ravens following the Bears' first possession of the second half. With the first-round pick unavailable, Andy Dalton will start against the Lions and fellow veteran Nick Foles will serve as his backup.
In relief of Fields against the Ravens, Dalton completed 11 of 23 passes for 201 yards with two touchdowns and a 107.3 passer rating.
Thursday's start will be Dalton's first since Week 2 when he sustained a knee injury in a 20-17 victory over the Bengals at Soldier Field. This season he has played in four games with two starts, completing 65.8 percent of his passes for 471 yards with three touchdowns, one interception and a 91.8 passer rating.
Hicks will miss his second straight game after getting hurt in the Bears' 29-27 loss to the Steelers Nov. 8 in Pittsburgh. This season he has registered 18 tackles, three tackles-for-loss and 1.5 sacks.
Receiver Allen Robinson II is listed as doubtful and likely will also sit out his second consecutive game. He hurt his hamstring against the Steelers while making a 39-yard catch on a late go-ahead touchdown drive. Robinson also would have been unable to practice all week.
Four Bears are questionable: Safety Eddie Jackson (hamstring), defensive end Mario Edwards Jr. (ribs), safety Tashaun Gipson Sr. (chest) and receiver Marquise Goodwin (shoulder). Jackson and Edwards would have been limited in practice this week, while Gipson and Goodwin would have been full participants.
In other news Wednesday, the Bears flexed receiver Isaiah Coulter and outside linebacker Sam Kamara from the practice squad to the active roster.
Coulter made his Bears debut last Sunday against the Ravens, playing just one snap on offense. He was signed Aug. 22, waived during final cuts and re-signed to the practice squad, where he spent the first 10 weeks of the season. Before joining the Bears, he had appeared in one NFL regular-season game, playing six snaps on offense for the Texans last Dec. 13 in a 36-7 loss to the Bears at Soldier Field.
Kamara, who signed with the Bears this year as an undrafted free agent from Stony Brook, has appeared in four games as a rookie, all as a reserve, registering four tackles on defense and one on special teams.