Trubisky suffered a shoulder injury late in Sunday's win over the Vikings.
The coach says it is possible that Trubisky could play against the Lions without practicing all week.
Daniel hasn't started or played extensively in an National Football League game since 2014, and might start for Trubisky because of a right shoulder injury sustained in the fourth quarter of Sunday night's 25-20 Bears victory over the Minnesota Vikings.
When Nagy said that Trubisky couldn't practice on Tuesday, that's when Trubisky's next start began looking dicey.
Trubisky will sit out on Thanksgiving, and Chase Daniel is getting a spot start in his place. Daniel, 32, is a career backup who began his career with New Orleans in 2010 and has completed 65.4 percent of his 78 passes with one touchdown and one interception. "I know that. But we've got to make sure in these situations that we're doing the right thing".
Nagy added that the team doesn't believe the injury is a long-term issue.
"It was really hard for him when he decided - and we knew - that this isn't the right thing", Nagy said.
Trubisky threw one more pass and finished the game. Trubisky is dealing with a shoulder bruise and if it was a Sunday game, he'd probably play.
Daniel hasn't thrown a regular-season pass since 2016.
The Lions haven't had much time to prepare for this game after playing last weekend, but the Bears had even less time to recover, since their Sunday game against Minnesota was at night.
"Nags and I go way back, he was my position coach for three years in Kansas City, obviously, and we stayed close for my time away", Daniel said.
Detroit (4-6) is in the middle of a three-game homestand that began with a victory over Carolina last weekend, but rookie running back Kerryon Johnson left that game with a knee injury.
"We're not going to change the offense if something happens".