Portis left the game with 3:20 remaining in the first quarter after a helmet-to-helmet hit from Falcons safety Thomas DeCoud. The Redskins announced after the injury Portis would not return. There was no penalty on the hit.
"We're going to be cautious with it," Redskins coach Jim Zorn told the team's official Web site.
Portis was helped to his feet after being checked by the medical staff on the field. He appeared shaky at first, but then walked off the field with a towel over his head.
It was Campbell's second injury of the game. He left with a chest problem after he was sacked for the fifth time in the first half. He returned for the start of the second half.
Todd Collins replaced Campbell after each injury.
Falcons receiver Brian Finneran left the game in the first quarter with a knee injury and did not return. There were no immediate details on the severity of the injury.
The Associated Press contributed to this report