Williams' agent confirmed the injury to Josina Anderson after Ian Rapoport of NFL Network first revealed the diagnosis, noting Williams is "going to try to play through it after rehabbing for a few weeks."
An undrafted free agent out of Western Oregon, Williams has stepped into the Raiders lineup and become a reliable target for quarterback Derek Carr. He tallied 42 catches for 651 yards and six touchdowns last year and isn't that far removed from the 1,059 receiving yards he posted in 2016 with the San Diego Chargers.
"It's kind of nice having somebody like that, but he can run these routes and set people up and knows he's a technician also," Carr told reporters of Williams' ability to stretch the field. "He's not just a big, raw body.
"To be able to hit those deep shots, the only thing it's going to do is help our running backs, it's going to help our offensive line. So it's nice to have someone with that skill set."
The Raiders also have Henry Ruggs III and Hunter Renfrow among their wide receivers, but Williams is a proven target.