Williams caught a pass in the third quarter and went to make a juke move to get by Vikings safety Harrison Smith. But Williams planted his left leg, fell, and was tackled from behind. Williams remained on the field and limped off while being helped by trainers. He was then carted back to the locker room with a towel covering his head. Williams was also carted to the team bus postgame.
Williams was having his best game of the season with seven catches for 121 yards and one touchdown before the injury. Chargers coach Brandon Staley said after L.A.'s 28-24 win that there was "no update" on Williams' injury.
This injury comes after Williams returned this year from a back fracture he suffered on a hit he took in the final three minutes of the Chargers' regular-season finale against the Denver Broncos last season.
If Williams misses an extended period, that will likely make Chargers rookie first-round receiver Quentin Johnston much more involved in the offense. Johnston has had the slowest start of the four first-round receivers, as he sits on the depth chart behind the Chargers' more experienced receivers in Keenan Allen, Joshua Palmer and Williams.
On Sunday, he played 16 snaps and had two catches for 10 yards, his highest yard total this season.
"It felt good, just there to help any way I can," Johnston said after the game. "It was in a weird situation with Mike going down. We still got prayers going out for him. But it felt good just to get a rhythm in the game ... I came in behind some great guys and in my receiver room, and I feel like up to this point, I picked up enough to go out there and show what I can do."