The 12th-year veteran played in pain last season and was diagnosed with a stress fracture in a small bone near his ankle in February. He underwent surgery in March and returned to practice Aug. 1.
But the pain didn't subside, and Lake had to reevaluate his progress after X-rays showed the fracture hadn't fully healed. He decided bone-graft surgery was the best option. He'll have a piece of bone removed from his hip and attached to the foot.
Coach Tom Coughlin said the rehabilitation would take six months and the Jaguars would soon place Lake on injured reserve, a move that will officially end his season.
"It's what Carnell wanted to do," Coughlin said. "He wanted a chance to play the game injury free. It's an unusual injury, one that is not easy to heal."
The loss of Lake is another in a wide assortment of injuries the Jaguars have encountered this preseason.
Right tackle Leon Searcy is out until at least November after tearing a tendon above his right knee. Five other offensive linemen, including three starters, have missed good portions of training camp.
With Lake out, Rayna Stewart and Mike Logan will compete for the starting free safety spot.
Lake, a five-time Pro Bowl player who signed with the Jaguars before last season, brought maturity, experience and an understanding of coordinator Dom Capers' strategies to a defense that sorely needed it.
After spending two years in the lower third of the NFL in defense, the Jaguars improved to fourth last season.
This is the first major injury for Lake, who has missed only six games over 11 NFL seasons. He was not available for comment.
"I believe he wants to refocus, have enough time to prepare himself, and that's why the surgery right now is the way we're going to go," Coughlin said.
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