PITTSBURGH --- The Pittsburgh Steelers haven't been this thin at running back since losing 1,000-yard rushers Franco Harris and Rocky Bleier to injuries before the 1976 AFC Championship Game.
With Willie Parker and Rashard Mendenhall injured and out, the division-leading Steelers are down to one healthy running back for Sunday night's key AFC game in Jacksonville -- Mewelde Moore, who had only one carry in their first three games.
Parker, coming off three consecutive seasons with 1,200 or more yards, will miss his second game in a row with a strained knee. It still isn't certain if Parker will be ready for the Oct. 19 game at Cincinnati, which follows an off week.
"We live week to week and day to day," coach Mike Tomlin said Tuesday, barely 12 hours after a 23-20 overtime victory over AFC North rival Baltimore. "We're going to Jacksonville this weekend and we need somebody to tote the thing."
The injuries may force the Steelers to sign two running backs -- an unusual move at this stage of a season.
Former backup Najeh Davenport may return and Gary Russell, a former University of Minnesota back who spent the 2007 season with them, could be promoted off the practice squad.
Carey Davis, the fullback, also has a sprained ankle and may not play Sunday night.
"Rest assured we will play with a running back this week," Tomlin said.
Parker's injury gave first-round draft pick Mendenhall a chance to make a major contribution as a rookie, but he needs surgery for a fractured right shoulder and will miss the rest of the season. Mendenhall was hurt while being hit by Ravens linebacker Ray Lewis during his first career start.
Right guard Kendall Simmons also ruptured an Achilles' tendon on Monday and won't play again this season. Even before Mendenhall and Simmons were hurt, the Steelers were without Pro Bowl nose tackle Casey Hampton (groin) and defensive end Brett Keisel (calf).