Jack Thomas/Getty Images

The Oakland Raiders reportedly fear safety Karl Joseph suffered a "serious" foot injury during Thursday night's 26-24 victory over the Los Angeles Chargers.

Ian Rapoport of the NFL Network reported the Raiders are awaiting MRI results for an official diagnosis and a potential timetable for how long Joseph could miss.

The 26-year-old West Virginia product suffered the injury in the process of making an interception with 20 seconds left in regulation to secure the Oakland win.

Joseph was walking with crutches after the game, but he hoped Friday's tests would reveal nothing major.

"Hopefully I'll be all right," he told reporters.

Raiders head coach Jon Gruden sounded less optimistic when discussing the health of both Joseph and fellow safety Lamarcus Joyner, who suffered an apparent hamstring injury on the same possession.

"Worried about Joyner. Really worried about him. Worried about Joseph," Gruden said.

Losing those two key cogs in the secondary would be a major setback for an Oakland pass defense that's already struggled this year, ranking 30th in passing yards allowed per game (283.2).

The Raiders, who own a 5-4 record after the win, do have three extra days off since they played on Thursday Night Football. Their next game isn't until Nov. 17 against the Cincinnati Bengals, but it's unclear whether that will be enough time for either Joseph or Joyner to recover.

Curtis Riley and Erik Harris would be called on to start at safety if both players are sidelined.