The Falcons signed CB Terrance Johnson Tuesday and placed CB Brent Grimes on injured reserve. Grimes suffered an Achilles injury in the season opener.
Johnson played in 10 games with the Colts in 2011 and had two starts. He recorded 37 tackles. He originally entered the league as an undrafted rookie in 2010.
Grimes was playing under the franchise tag this season. He has 13 career interceptions and 56 passes defensed.