Ragnow will miss time with a toe injury. Per NFL policy, players can return from the team's injured reserve list after missing at least three games.
"He's got, basically, a version of turf toe right now is what he's got," Lions coach Dan Campbell explained on Monday. "We'll know a lot more this afternoon with him. I would say he's probably going to be out, though."
Ragnow suffered the injury during the first half of Sunday's loss at Chicago. In the same game, the team lost outside linebacker Romeo Okwara to a season-ending Achilles injury.
Ragnow earned his first Pro Bowl berth last season and became the NFL's highest-paid center this offseason.