The Baltimore Sun reported that Flacco could be limited early in camp while nfl.com took it a step further, saying Flacco is preparing to miss 3-to-6 weeks with a disc issue in his back.
Veteran backup Ryan Mallett and Dustin Vaughan are the only other quarterbacks on the Ravens roster heading into camp.
Ravens coach John Harbaugh is expected to speak with reporters after Thursday's practice while the 32-year-old Flacco is scheduled to speak to the media after Friday's workout.
Flacco is set to enter his 10th season. Last season, he threw for 4,317 yards with 20 touchdowns and 15 interceptions. For his career, he has thrown for 32,639 yards with 182 touchdowns and 117 interceptions. He also has a 61.5 percent completion percentage and a 84.5 passer rating for his career.