Michel, who had elevated to a top spot on the depth chart alongside "passing back" James White, will be considered week-to-week, the source told Schefter.
This is a best-case scenario for Michel and the Patriots after he was helped to the sideline and then carted to the locker room early in the second quarter of the team's 38-31 win over the Chicago Bears on Sunday.
In his standard day-after-game conference call, head coach Bill Belichick said he didn't have anything to add about Michel's status, noting that the team will update its injury report the next time it is required to do so later this week.
During his weekly interview on sports radio WEEI, Belichick said the team will explore the possibility of adding a running back.
"We'll take a look at that over the next day or two and try to figure it out so when we start practicing for Buffalo, we'll be ready to go," Belichick said. "We'll look at our options and see what we feel like the best thing is [and] see how long we think Sony might be out."