Coach Mike Mularkey says Lowery will miss the team's Oct. 21 game at Oakland and maybe the following week at Green Bay. The Jaguars (1-4) are off this week.
Mularkey says second-year safety Chris Prosinski will start in Lowery's place.
Lowery ranks fourth on the team with 33 tackles and has three passes defended.
The Jaguars hope to have safety Dawan Landry (knee), defensive end Austen Lane (foot) and defensive end George Selvie (knee) back against the Raiders. Landry and Lane missed practice Wednesday. Mularkey isn't sure about linebacker Daryl Smith (groin) and receiver Laurent Robinson (concussion). Both sat out practice Wednesday. Robinson has yet to pass his post-concussion test.