The second-year safety was diagnosed with a stress fracture of the fifth metatarsal of his right foot and will continue to be evaluated, the team announced.
James will be out a significant amount of time, but how much remains to be determined, NFL Network Insider Ian Rapoport reported, per a source.
Chargers coach Anthony Lynn told reporters Friday there is no timetable for James to return and that he expects him to play in 2019, but he can't say for sure. Lynn didn't rule out surgery or a trip to injured reserve for James, who suffered the injury Thursday at practice.
"We're going to miss him a lot," Lynn told reporters. "But we're a team. We have a good team and we have guys that will step up, and we'll be fine."
After just one season in the NFL, James has established himself as one of the most highly regarded safeties in football.
As a rookie, he earned All-Pro and Pro Bowl distinctions, notching 105 tackles (75 solo) to go with three interceptions, 13 passes defended and 3.5 sacks, building a reputation for standout play against the run, in coverage and even rushing the quarterback. James is one of just eight rookie defenders named first-team All-Pro since the 1970 merger, per NFL Research.