The Steelers re-signed Carey Davis, who started 11 games at fullback for them in 2007-08 but was released when the team set its 53-man roster at the beginning of the month.
Davis takes Frank Summers' place on the roster.
The Steelers put Summers on the reserve/injured list because of a back injury, ending the rookie's season.
The loss of Summers, who saw a doctor yesterday, isn't the only reason the Steelers brought Davis back.
Tight end David Johnson, who also lines up at fullback, sustained a high ankle sprain in a 23-20 loss to the Bengals. Coach Mike Tomlin said the rookie is "questionable" for Sunday's game against the visiting San Diego Chargers.