Wells was held out with a bruised right knee. Tim Hightower is the starting running back.
Wells was limited in practice all week. He gave the knee a strong test on Thursday and insisted afterward that he would "definitely" go through a full practice on Friday. But the knee swelled up, again limiting Wells in practice on Friday.
The second-year pro from Ohio State, Arizona's leading rusher last season, sat out last week's season-opening victory at St. Louis. He was injured against the Washington Redskins in the final preseason game on Sept. 2.
The Falcons will be without starting strong safety Erik Coleman, who is out with a left knee injury he suffered in last week's loss at Pittsburgh. Second-year safety William Moore made his first start.
Information from The Associated Press was used in this report.