Pittsburgh Steelers linebacker James Harrison did not practice on Thursday due to a knee injury.
Harrison had taken limited reps on Wednesday, but was downgraded just three days before the season opener against the Denver Broncos.
In addition, running back Baron Batch missed practice after seeing limited action one day prior.
Safety Ryan Clark, who participated in practice for a second straight day, is guaranteed to miss the Sunday night contest in Colorado's capital due to a blood disorder which makes it impossible to play at high altitudes.
One player who made a return was linebacker Larry Foote, whose ankle caused him to miss Wednesday, but on Thursday he was able to take full participation.