They don't expect to shut him down for the rest of the season.
Lions coach Jim Schwartz said Wednesday that Daunte Culpepper will start at Baltimore and Stafford will likely be the No. 3 quarterback.
Stafford aggravated his left shoulder Sunday at Cincinnati.
"If he hadn't taken that hit in the fourth quarter of the Cincy game, we wouldn't be having this discussion," Schwartz said. "It was a very similar hit to the one that he took in the Cleveland game and we want to avoid the situation where it becomes something chronic.
"Structurally, everything is still on course. It's sore and we just wanted to avoid a continuing cycle of come back, get hit, come back, get hit. We'll give it time to rest and put it behind him," he said.
Schwartz acknowledged there's a chance Stafford will miss more than one game.
The No. 1 pick in the 2009 NFL draft gained some fame when he hurt the shoulder Nov. 22 against Cleveland. He put himself back in the game after getting injured and threw his fifth touchdown pass on an untimed play.
Stafford was miked for sound during the game NFL Films president Steve Sabol called it "the most dramatic player wiring ever."
He has thrown 13 TDs and 20 interceptions in 10 games.
Stafford missed two games with an injured right knee. Culpepper threw one TD and two interceptions in his two starts, both of which were losses.
Schwartz said the team did not consider starting Drew Stanton against the Ravens.
"Daunte is our backup quarterback," he said. "We've had no change in our depth chart. We have a lot of confidence in Daunte."
Schwartz, a first-year head coach, went against his previous policy of announcing only the required about of information about injured players.
"It is kind of against the grain from the way we've done things in the past, but there are some benefits to doing it this way also," he said.
Schwartz told Stafford and Culpepper about his plans and wanted both to avoid answering questions about the situation this week.
When Stafford got the start on Thanksgiving, Culpepper looked like he was upset because he expected to play.