Freeman, who suffered the injury during his debut appearance for the Vikings in a 23-7 defeat to the New York Giants on Monday, will undergo testing for concussion-like symptoms this week, but Frazier is working on the basis that he won't be fit.
That would open a space for Christian Ponder to start at quarterback, which has been a troublesome position for the Vikings this season with Ponder, Freeman and Matt Cassel all being included from the start for at least one match.
"Looking at the history of guys who have concussions on a short week that are able to at least get cleared for Sundays, we'll have to proceed as if [Freeman]'s not going to make it," Frazier told reporters.
"It's important. That quarterback position, you want to know who's going to be lining up, week in and week out. But that's the circumstance where we are, and Christian will do a good job for us on Sunday night."
The Vikings are currently bottom of the NFC North, with their only victory so far this season coming in the International Series match against the Pittsburgh Steelers at Wembley.