#Broncos LB Brandon Marshall, one of their big-time performers this year, suffered a mid-foot sprain, source says.— Ian Rapoport (@RapSheet) December 15, 2014
Ronnie Hillman had a foot sprain and his original prognosis was 4-6 weeks. If Marshall's injury is similar, 4 weeks out would be the Divisional round of the playoffs, 5 weeks would be the AFC Championship Game, and 6 weeks would be the bye week before the Super Bowl. This is just speculation, however.
After all the Lisfranc injuries that Broncos players have suffered the past couple of seasons, it is natural to be paranoid about that possibility, but again there simply isn't enough information out there yet to be able to say definitively one way or another what Marshall is suffering from.
John Fox will address the media this afternoon and will be in a better position to offer more information. Until then vague and unknown will be the words of the day.