The Steelers have placed Summers on IR. On Tuesday, Coach Mike Tomlin said Summers had a "mysterious" back ailment and was visiting with a doctor.
Davis made the team in 2007 and started 11 games at fullback over two seasons. He rushed for 35 yards on 12 carries last season and caught five passes for 27 yards. In 2007, he gained 68 yards on 17 carries and caught 12 passes for 49 yards.