During the first quarter, the Bears were deep into their own territory when Bears quarterback Caleb Hanie handed the ball to Forte. Forte cut outside trying to find some open room.
Chiefs linebacker Derrick Johnson exploded through the Bears' offensive line and launched his helmet into Forte's right knee. Forte was then seen writhing on the field in excruciating pain.
While Forte did walk off the field under his own power, he went into the locker room and did not return.
The Bears cannot afford to have Forte out for a significant amount of time, as starting quarterback Jay Cutler is also sidelined with a broken thumb on his throwing hand.
Forte is the heart and soul of the Bears' offense, being deadly in both the running and passing games. He has 1,475 yards of total offense, accounting for 37.7 percent of the Bears' yards.
Defenses keyed to stop Forte with eight men in the box because Hanie is an inexperience and unproven starting quarterback. If Forte is lost, Chicago has a huge drop off in talent with Marion Barber and Kahlil Bell.
Barber is a solid change-of-pace back who is good for goal line and short yardage situations. However, the veteran hasn't been the last few years and was nothing special in that role.
Bell, a third-string backup who plays special teams, does not have the size to be primary backup and has 11 rushes for 23 yards this year.
Chicago rolled to a 7-3 record and an NFC Wild Card spot when Cutler and Forte were working together. Now, the Bears will labor through hard times with no offense standouts leading the unit.