Williams is expected to be ready for training camp next season, a source told ESPN's Adam Schefter.
"It's the toughest kind of news. You know, Mike's one of my favorites," coach Brandon Staley said. "He's one of our most important players and he's a guy who not only is one of our best players, but he sets the example I think from a team-building culture standpoint in terms of how you want to work.
"We're going to make sure that this group plays to his standard and that's our responsibility now."
Williams has been one of the Chargers' top targets since he entered the league in 2017. In March 2022, the Chargers rewarded Williams with a three-year, $60 million contract.
Williams left Sunday's game against the Vikings in the third quarter on a medical cart. He 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 was having his best game of the season with seven catches for 121 yards and one touchdown before the 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.
The season-ending injury to Williams should increase snaps and targets for rookie first-round receiver Quentin Johnston, who has just five receptions for 26 yards through three games.