The chances are not much better that Steelers safety Troy Polamalu will play against the Raiders on Sunday, though the team will have a better idea on his status Friday.
The team will be on its bye in Week 4.
Steelers coach Mike Tomlin said on Tuesday that Harrison, who is recovering from right knee surgery, and Polamalu, who is dealing with a strained right calf, would have informal workouts this week.
Harrison hasn't played since a playoff loss in Denver nine months ago, while Polamalu's calf didn't respond quickly to treatment last week after sustaining the injury in a season-opening loss to the Broncos.
The duo hardly was needed in a 27-10 romp over the New York Jets on Sunday. The Steelers (1-1) shut down New York in the second half, holding the Jets to just 91 yards over the final two quarters to win going away.
Information from The Associated Press was used in this report.