Here is the report from NFL.com from October 8.
NFL.com Chiefs News
(Oct. 8, 2006) -- Kansas City Chiefs Pro Bowl running back Larry Johnson was injured on a facemask tackle at the end of a 78-yard pass play late in the Week 5 game against the Arizona Cardinals.
Johnson broke free down the left sideline after the short pass. The Cardinals' Antrel Rolle grabbed Johnson by the facemask and the running back's head was twisted as he fell out of bounds at the Arizona 8. He lay motionless for a moment, but eventually got up and left the field under his own power.
Rolle was called for a personal foul on the play.