Williams suffered the injury on the second drive of the team's season opener against the New Orleans Saints last Sunday. Though he returned in the fourth quarter, playing 10 total snaps in the game, Williams said he was still sore the next day and would see how things went in terms of his availability against the Rams.
The 30-year-old Williams said the injury occurred when a defensive lineman fell on him during a tackle.
"Oh man, all 300 pounds on that little baby rib, man. That's all it was, man," Williams said Monday. "All 300 pounds on that little baby rib, man. It got me, though. It got me."
Williams, who was expected to split time with Cordarrelle Patterson as the team's primary rushers this season, had totaled 2 yards on his first two carries. Patterson, in Williams' absence, had career highs in carries (22) and rushing yards (120) against the Saints.
Williams signed with Atlanta after playing with the Chicago Bears last season. In his eight-year career -- he opted out in 2020 due to COVID-19 concerns -- he has played in 98 games with 336 carries for 1,397 yards and 14 touchdowns.
With Williams out at least a month, the Falcons are likely to turn to rookie fifth-round pick Tyler Allgeier out of BYU. Allgeier got some work with the first team during the preseason but was inactive last Sunday against the Saints. Atlanta could also look to converted cornerback Avery Williams, who made the full-time move to running back this offseason and is the team's punt returner, or to Caleb Huntley, who was given a standard elevation Saturday from the team's practice squad.
The Falcons also elevated defensive lineman Abdullah Anderson from the practice squad, completing a busy week for him. Anderson was released prior to Week 1 and then signed with the team's practice squad at the beginning of this week before being elevated Saturday.