Ridley was hurt when he was tackled by safety Jeremy Chinn at the end of a 19-yard catch-and-run late in the first half. He limped off the field and went to the locker room. He was originally listed as questionable to return but was ruled out early in the second half.
Interim coach Raheem Morris said after the game he had no update on Ridley.
Ridley, who had three catches for 42 yards at the time of his injury, entered the game as the Falcons' leader in receptions (40), receiving yards (615) and receiving touchdowns (six). The Falcons have relied on him heavily because Julio Jones missed two games with a hip injury.