Coach Mike Tomlin said the two-time Pro Bowl running back awoke Saturday morning with his back not feeling right. The Steelers were coming off their only night practice of training camp.
"It shouldn't be a big, major deal, but we wanted to exercise caution," Tomlin said.
Parker, 28, is coming off his worst season since becoming the Steelers' starting running back in 2005. Knee and shoulder injuries limited him to 11 games in 2008 and he gained 791 yards on 210 carries, averaging a career-low 3.8 yards per attempt.
The 5-foot-10, 208-pound Parker is heading into the final season of his contract and is expected to lose some carries to second-year running back Rashard Mendenhall. A first-round draft pick in 2008, Mendenhall missed most of last season with a shoulder injury.
Outside linebacker LaMarr Woodley sat out his third consecutive day of practice due to swelling in his right knee, but he expects to return Sunday.