Kansas City running back Kolby Smith injured his ankle and will probably not return to Sunday's game.
Smith made his first carry against the Pittsburgh Steelers and then limped off the field. He was activated two weeks ago after missing a year with knee surgery.
Pittsburgh guard Chris Kemoeatu injured his right knee and will not return to the game.
Team officials said Kemoeatu was hurt early in the third quarter. The Steelers were already missing Pro Bowl safety Troy Polamalu, who was not active because of a knee injury.