The Cowboys lost wide receiver Miles Austin to a hip strain in Thursday's 38-31 loss to the Washington Redskins. The Cowboys had some health issues, with Kevin Ogletree missing the Redskins game with a concussion.
Armstrong could be signed if Austin is added to the injury list.
"That would be really looking at where we are health-wise with our receivers and looking ahead with what we might need to do," Cowboys owner/general manager Jerry Jones said. "But we'll have to see what Miles looks like."
Armstrong, who is from Carrollton, Texas, was claimed off waivers by the Jacksonville Jaguars after his release by the Dolphins in October. But he was cut this week by the Jaguars on Nov. 12.
He didn't play in any games for the Jaguars but had three catches for 12 yards for the Dolphins this season.