"It's more doubtful than probable," coach Rod Marinelli said when asked about Culpepper's status.
Marinelli said an MRI on Culpepper's shoulder revealed a sprain.
Culpepper stretched with teammates Wednesday, then left the field and had to avoid a blocking sled a teammate was hitting toward him.
Drew Henson, Drew Stanton and Dan Orlovsky participated in drills led by quarterbacks coach Scot Loeffler and split reps during practice.
Orlovsky has been out since Nov. 2 with an injured wrist.
"It felt structurally strong. It felt better," he said. "I'm going to miss some throws because of it, but I'm pretty confident I'll be able to go out and play effectively."
Stanton has been sidelined since Nov. 23 with a concussion.
"I feel good now," he said.
Henson threw an NFL pass on Thanksgiving for the first time in four years and was sacked on the final play Sunday against the Vikings after they knocked Culpepper out of the game.
The Lions (0-13) seem destined to be the NFL's first 0-16 team, closing against the Colts, New Orleans and Green Bay.
Indianapolis, which has won six straight, is favored to win its 10th game of the year by more than two touchdowns against Detroit.
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