When Bell was suspended for the first two games, Williams shined in a starting role before being relegated back to a reserve. Now Williams' coach and teammates are expecting much of the same from the veteran with Bell out for the season and the surprising Oakland Raiders visiting Sunday.
Bell is on injured reserve after suffering a severe MCL injury in his right knee during last week's 16-10 loss to Cincinnati, the second straight defeat for the Steelers (4-4) that dropped them 3 1/2 games back of the unbeaten Bengals in the AFC North.
There isn't much worry that Williams can be a suitable replacement over the final eight games - and hopefully into the playoffs - despite Bell's success, not only in the running game but catching out of the backfield.
''He's an established, capable guy who we know can deliver,'' coach Mike Tomlin said. ''There's a great deal of comfort in knowing his capabilities.''
Williams, cut by Carolina in March after nine seasons, rushed for 127 yards in a season-opening loss to New England before scoring three touchdowns the following week in a win over San Francisco.
''We've been here before,'' Williams said. ''For about eight or nine years, I've been a starter in this league and I started the first two games in the season. I know why (the Steelers) brought me here and I'm going to play my role. If that's what they need me to do, then I'm going to do it.''
The loss of Bell came in the same game when Ben Roethlisberger returned after missing four with a left knee injury. He went 28 of 45 for 262 yards and a touchdown, but he also tossed three interceptions four the first time in four years.
Charles Woodson has been preying on that kind of inaccuracy. The 39-year-old leads the NFL with five interceptions for a Raiders team trying to return to the playoffs for the first time since winning the AFC championship in 2002.
''It's fine for some people to play from the underdog role, but I don't like it,'' said Woodson, who played for the Raiders' last Super Bowl team. ''I don't like being the underdog. I want to be expected to win games. I want these guys to go out there and be expected to win games. Yeah, it's a little premature to be thinking that far ahead, playoff-wise, but there's no reason you can't think of yourself as a playoff team.''
Carr, Cooper and first-year coach Jack Del Rio share in that philosophy. Carr has 15 touchdowns against only three picks after throwing for 333 yards and a career high-tying four scores in last week's 34-20 victory over the New York Jets.
Cooper finished with a season-low 46 yards but was shadowed by Darrelle Revis, who came away impressed by the No. 4 pick in the draft. Cooper has three 100-yard performances and is on pace to be the Raiders' first 1,000-yard receiver since Randy Moss in 2005.
''I feel like there's room to grow and that I can play so much better than I am right now,'' Cooper said.
Del Rio isn't shying away from praising his team. It ranks ninth in total offense at 365.3 yards per game after finishing dead last a season ago, and is one of five AFC teams with a record above .500.
''I don't really understand this question of guarding against (success). We're a 4-3 team,'' Del Rio said. ''We've battled each and every week. We're going to continue to battle each and every week. These kind of questions are kind of silly to me.''
Pittsburgh's defense ranks 26th against the pass, allowing an average of 269.5 yards per game. Oakland, though, is 31st, giving up 302.1 through the air despite Woodson's solid play.
"They're coming in here, it's going to be very physical," Roethlisberger said. "Their defensive backs like to do a lot of grabbing, holding, and just being physical in general. It's a really good test for our receivers and for me to be accurate."
Roethlisberger is 1-4 in his career against the Raiders despite posting a 97.5 rating and averaging more than 300 yards passing.