Parker missed practice for the second day in a row Thursday because of a shoulder injury -- not the sprained knee that kept him out of four games -- and will not play in Sunday's game against Indianapolis, the Pittsburgh Post-Gazette reported.
Parker, who rushed for at least 1,200 yards in each of the last three seasons, returned from his knee injury layoff to rush for 71 yards and a touchdown in a 23-6 victory over the Redskins on Monday night. Parker hadn't played since hurting his knee Sept. 21 against Philadelphia.
Ben Roethlisberger, dealing with a slightly separated right shoulder and a left pinkie ligament injury, also didn't practice Thursday. The Steelers quarterback is optimistic about practicing Friday and playing against the Colts, although he sat out the second half of the Redskins game.
Roethlisberger's throwing shoulder has bothered him since the opener, and he has skipped practices during multiple weeks without missing any games. He has played in all but one Steelers game since the opener in 2006.
The Associated Press contributed to this report.