Greig, who was a late scratch Wednesday versus the Sabres, is out due to an undisclosed injury, Bruce Garrioch of Postmedia reports.
Greig was not on the ice for warmups. There is an illness in the Senators' locker room, but the initial report indicates Greig is hurt, not sick. The 24-year-old can be considered day-to-day ahead of Saturday's home contest against the Mammoth.