Parker has missed three games with a sprained medial collateral ligament, but practiced earlier in the week and was expected to be ready for the matchup of teams with 5-1 records. He is listed as doubtful.
Parker would be replaced by Mewelde Moore, who began the season as the third-down back, but has rushed for 219 yards in the last two games. Moore gained 120 yards and scored three touchdowns, one on a pass reception, during a 38-10 win in Cincinnati last Sunday.
Until he was in the lineup in Jacksonville on Oct. 5, Moore had not started since he was with Minnesota in 2005.
Two other Steelers starters also didn't practice Friday: left tackle Marvel Smith, who will miss a second successive game because of back spasms, and defensive end Aaron Smith.
Smith, one of the top players on the Steelers' league-leading defense, has not practiced all week for undisclosed reasons. Normally, Steelers players who do not practice all week do not play in that game, but Smith is listed as questionable.
Pro Bowl safety Troy Polamalu practiced Friday and is expected to play. He incurred at least the seventh concussion of his career during the Cincinnati game.