They get an elite pass-catcher at a crucial time, coming off a 34-3 beating in Philadelphia. And Kansas City's talented front seven is lurking Sunday night.
Just listen to center Maurkice Pouncey.
"It's going to be huge. It changes the passing game," Pouncey said of Bell, who served a three-game suspension for a violation of the league's substance-abuse policy.
DeAngelo Williams was brilliant for most of the past three games, and he should remain involved in the offense. But the loss to the Eagles showed this team needs more receiving options downfield after the loss of Martavis Bryant for the season.
Bell is almost like a glorified slot receiver, catching 83 passes for 854 yards in 2014, his last full season. Bell has great vision as a runner, but his skill set translates just as well to the passing game. He gives offensive coordinator Todd Haley plenty of options to mix and match looks.
Perhaps the addition of Bell can help bridge the gap after a supporting cast of receivers struggled behind Brown.
Roethlisberger was 12-of-18 for 140 yards when throwing to Brown on Sunday, and 12-of-26 for 117 yards and an interception when throwing to Williams, Sammie Coates, Eli Rogers, Jesse James, Markus Wheaton or Darrius Heyward-Bey.
To be sure, Big Ben wasn't at his best. He missed some throws.
Wheaton's lackluster debut punctuated the notion that the Steelers could use one more piece. Wheaton was frustrated after dropping multiple passes, including a potential touchdown. "I just didn't perform," he said.
Coates has had bright moments while averaging 29 yards a catch, and Rogers is promising in the slot, but it wasn't nearly enough Sunday. Week 2 against Cincinnati was a struggle at times, too, but at least Pittsburgh kept the Bengals honest with Williams' 94 rushing yards on 32 carries.
Big Ben lamented the Eagles' success in making Pittsburgh one-dimensional. Williams finished with 21 yards on eight carries, 13 of which came from one rush.
"We pride ourselves on getting four-plus on first down," Roethlisberger said. "We've been able to do that so far this year. When you can't do that, you get behind in the chains and they start dropping into zones, getting pressure with their front four. Makes it tough."
Pouncey could see the Steelers "most definitely" using Williams and Bell in the same backfield. If that's the plan, don't be surprised if Bell moves across the formation as a receiver, possibly as a threat in the intermediate-to-deep-ball range. Bell ran some deep routes in training camp.
Now Bell's knee is fully healed, and he'll be hungry for chunk plays in a contract year. Every yard gained will put more distance between himself and his past issues.
Bell couldn't be joining his team at a better time, especially when the defense is this salty.
"We play like this, we're not going to win any games," defensive end Cam Heyward said.