James went down with the injury during Sunday's practice and is expected to be out six-to-eight months. The Chargers said they expect him to be fully recovered for the 2021 season.
James, a first-team All-Pro and Pro Bowler during his rookie season, missed 11 games in 2019 with a stress fracture in his foot.
"Derwin is a strong-minded person and nothing can really break him down," said Chargers defensive end Melvin Ingram III, per Alden Gonzalez of ESPN. "This is just another chapter in his story, which is gonna make his story so much better at the end."
James was expected to be the anchor of a strong Chargers secondary but will instead leave a sizable gap at strong safety. Desmond King or Alohi Gilman will likely get the first look at moving into the starting lineup. Chargers coach Anthony Lynn said the team is not considering signing Earl Thomas, who was released by the Baltimore Ravens last week.
"Since you guys are constantly telling me how stacked my secondary is, why the hell would I be looking anywhere else?" Lynn told reporters in response to questions about Thomas.
James and Thomas play different safety positions, but Los Angeles defensive coordinator Gus Bradley does have familiarity with Thomas dating back to their days in Seattle.