Pettis injured his left knee at Wednesday's practice, Cam Inman of The San Jose Mercury News reports.
Pettis suffered the injury during a special-teams drill and was eventually listed as a non-participant on the 49ers' first practice report of Week 13, according to Eric Branch of the San Francisco Chronicle. Nothing more is known about the nature or severity of Pettis' health concern, meaning his status will continue to be monitored as the weekend draws closer. After a strong debut season for San Francisco, Pettis has tumbled down the depth chart at receiver in 2019, logging just seven offensive snaps in total over the past two weeks.