Jamaal Charles will undergo tests to determine the extent of the knee injury, which forced him out the Kansas City Chiefs' 18-17 loss against the Chicago Bears on Sunday.
The running-back was helped from the field early in the game at Arrowhead Stadium after appearing to trip over his own leg during a Kansas drive.
However, Andy Reid told reporters after the game that the Chiefs fear Charles could be out for the rest of the season, with a possible tear of his anterior cruciate ligament.
The Chiefs, who are at 1-4 in the AFC West after the defeat to Chicago, travel to the Minnesota next week.
