Coach Bobby Petrino said the team was concerned that Coleman and Lewis might risk serious injury if they continued to play.
Coleman, a Pro Bowl selection two years ago who led NFL interior linemen with 52½ sacks from 2001-07, hurt his hand and triceps in Atlanta's 31-7 loss to Tampa Bay last week.
Lewis, a rookie drafted in the sixth round out of Washburn University, suffered a knee injury that will require surgery.
The Falcons might regret the move last month to release nose tackle Grady Jackson, an 11-year veteran who led the league with 13 stops for lost yardage in 2006 and had 5½ for negative yardage in Altanta's first seven games.
Lewis replaced Jackson, who now plays for Jacksonville, on the first-team defense.
Atlanta is so short of experience on the interior line that third-year reserve end Chauncey Davis will be used as a tackle if necessary for certain defensive alignments.
The loss of Coleman, a nine-year veteran, was not unexpected after he rehabbed furiously to return from surgery on a torn quadriceps sustained in April.
Petrino first realized Coleman's injury when he walked through the locker room during the NFL draft and saw the 297-pounder lying on a training table. Coleman had sustained the tear while driving a personal watercraft.
Though Coleman insisted that his quadriceps held up well, he later hurt his right knee, which swelled up dramatically after his return to practice in September.
Babineaux, a second-round draft pick in 2005 from Iowa, has played in eight games this year, missing two with a knee injury. He and Stanley have combined for 25 tackles, two sacks and one fumble recovery.