Per Rapoport, the injury is a "serious one" and that "it's not good" based on an initial evaluation. However, more will be known Wednesday following an MRI.
ESPN's Adam Schefter reported Miller will likely need season-ending surgery.
Rapoport provided additional details following the MRI:
Miller reached his sixth straight Pro Bowl in 2019 but had a somewhat down year by his high standards. His eight sacks were the second-fewest of his career.
In general, it was a disappointing season all around as the team finished 7-9 and missed the playoffs for the fourth straight year. Adding salt to the wound, Shaquil Barrett finished with an NFL-high 19.5 sacks after leaving Denver to sign with the Tampa Bay Buccaneers.
Having Bradley Chubb back healthy and on the opposite edge will help offset the loss of Miller somewhat. But the 31-year-old is the unit's leader and best player. His absence will be a blow for Denver, which was already an outsider in the AFC postseason race.