ESPN's Adam Schefter added that Green Bay is now uncertain of how long the Stanford product will be out.
Montgomery had five carries for 28 yards on the opening series of the game before leaving with about 10 minutes left in the first quarter.
"Really, every injury is different", Packers coach Mike McCarthy said Friday. While Montgomery is a converted wide receiver, he tallied 457 rushing yards and three touchdowns on the ground previous year and helped bolster what was otherwise an uninspiring ground game after Eddie Lacy's injury.
If Montgomery and Williams were to miss next week's game with the Dallas Cowboys, Jones would likely be the starter.
Former Chiefs RB Larry Johnson Says He Is Living With CTE
His death brought to an end the controversial saga of a talented young player who couldn't seem to escape trouble off the field. More research is needed on genetics and mental illness and, well, anything else that might gum up the debate.
As with most rookies who aren't seen as franchise-shifting pieces right away, fantasy players should proceed with some level of caution with Williams even after Montgomery's setback.
The Packers next play at Dallas on Sunday, Oct. 8. Montgomery has also caught 18 passes for 129 yards and one touchdown.
However, Williams' talent alone makes him worth a waiver-wire pickup if he is still available.
He was replaced by rookie Jamaal Williams, who was knocked out midway through the second quarter with a knee injury.
Both running backs are rookies. He also became a more visible target in Green Bay's passing game under his new role, finishing the season with 44 receptions for 348 yards.