The Raiders worked out free-agent kickers Dave Rayner, Rhys Lloyd and Ricky Schmitt on Friday, according to league sources, and Janikowski's injury may be severe enough to shelve him for a while.
"We'll see as we continue to move forward but my goal is to make sure I have enough players to play and healthy bodies that can get the job done," coach Hue Jackson said before going to watch the kickers. "It's a huge part of our football team if (Janikowski) can't go. We'll get somebody that can. That's the way it goes."
Janikowski, who was limited in practice Thursday, is 12 for 13 on his field-goal attempts this season, including a 63-yarder he hit against the Denver Broncos to tie an NFL record.
The Associated Press contributed to this report.