Matthews could have signed with another team as an unrestricted free agent.
DiMarco has played in 30 games with 14 starts with Atlanta. He has 17 catches for 111 yards and one touchdown and has no career carries.
Matthews, a sixth-round pick in 2011, had six tackles in seven games last season. He has no career starts and has played primarily on special teams.
The team also signed wide receiver Nick Williams, who appeared in five games as an undrafted rookie with Washington in 2013. He had a brief stint on the Redskins' practice squad last season.
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