Coach Gus Bradley says starter Alan Ball is "highly unlikely" to play because of a biceps injury. Ball traveled to San Francisco for a second opinion earlier this week, but the Jaguars (1-6) don't expect it to be a season-ending injury.
Making matters worse for Jacksonville, Ball's replacement, Dwayne Gratz, left practice Thursday with hip flexor tightness.
The Jaguars already will be without starting linebacker Paul Posluszny, who is out for the season with a torn pectoral muscle, and defensive end Andre Branch. Branch will miss at least six weeks with a groin injury.