The 24-year-old appeared to be knocked unconscious immediately ... with his arms stiffening in the bent position.
Trainers rushed out to the football player ... and unscrewed his facemask, before securing him to a backboard and placing him on a stretcher.
I've spoken to multiple brain injury experts and no one is confident in the diagnosis for Donald Parham Jr.'s shaking arms here based on this video. But it's not good. The team at @ConcussionLF is hoping for the best possible outcome. pic.twitter.com/c3jTZ8DuPn
"I'm just hoping for the best," star quarterback Justin Herbert said of Parham after the game. "Parham has been an incredible teammate and an incredible friend. He's been nice to everyone in that locker room, and everyone loves him."
Parham has started nine games for L.A. this season ... scoring three touchdowns.