Fellow running back Tra Carson received a waived/injured designation from the Bengals (2-0), who are expected to be without Joe Mixon for two-to-four weeks as he recovers from minor knee surgery.
An undrafted rookie in 2015, Rawls rushed for 830 yards and had a league-leading 5.6 yards per carry as a fill-in for injured running back Marshawn Lynch during his first season with the Seattle Seahawks. He then set a franchise playoff rookie record with 161 rushing yards against the Detroit Lions in the NFC wild-card game.
The 5-foot-9 Rawls has been unable to stay healthy the last two seasons, however. He was expected to serve as the starter after Lynch departed, but Rawls started only 10 games in the following two years.
Rawls missed significant time in 2016 because of a fractured fibula, and he rushed for 349 yards with a 3.2 yards-per-carry average in nine games that season. Rawls had only 58 carries and averaged 2.7 yards per carry in 12 games, including three starts, in 2017.
The 25-year-old Rawls was let go during the final round of cuts by the New York Jets this summer.
Carson sustained a hamstring injury on Monday, per Bengals head coach Marvin Lewis.