Coach Sean McDermott said Friday that Allen is "hour-to-hour" with a right elbow injury. He has yet to participate in practice this week, including Friday, after sustaining the injury during the final drive of the Bills' 20-17 loss to the New York Jets on Sunday.
"We are in an hour-to-hour situation here to see how he progresses through the day," McDermott said on WGR 550.
Former Vikings quarterback Case Keenum would draw the start should Allen be unable to play for the Bills (6-2).
While Allen's availability is in question, McDermott ruled out safety Jordan Poyer and defensive end Greg Rousseau for the contest versus the Vikings (7-1).