It won't be from spectacular play by his young replacement, Dennis Dixon, because he's just that -- young. It won't be from spectacular play by either of his more experienced understudies, because Byron Leftwich is still recovering from a knee injury and Charlie Batch is probably too old to make a major difference. It won't be from an exceptional rushing attack, although Rashard Mendenhall does show he's capable of the occasional game-breaking run.
No, the Steelers' ability to weather Roethlisberger's four-game suspension for violating the NFL's personal-conduct policy will depend on the same thing that has long played a critical role in the franchise's record six Super Bowl victories: Dominant defense.
That's what did the most to allow the Steelers to begin the season with a surprising, 15-9 overtime win against the Atlanta Falcons, a popular preseason pick to unseat the defending Super Bowl champion New Orleans Saints as top dogs in the NFC South. And the Steelers are going to need to be every bit as effective on that side of the ball when they face the Tennessee Titans on Sunday and in the two other games they're without Roethlisberger.
"We definitely want to make it as easy as possible for our offense, give them a short field and try to get a couple of turnovers for them," linebacker James Farrior said. "We always feel that way anyway. Even if Ben was still around or he was our starting quarterback, which he'll be when he gets back, we definitely try to put the team on our back. We definitely take most of the responsibility as far as winning games and losing games.
"We always feel like if we give our offense a chance and put them in position (to score), we'll have the best chance to win. It's definitely always a challenge for us, and we try to rise to that occasion every week."
You can't do it a whole lot better than Pittsburgh's defense -- bolstered by the return of safety Troy Polamalu and end Aaron Smith from major knee and shoulder injuries they suffered last season -- did against the Falcons.
Atlanta's only points came on three Matt Bryant field goals. The Steelers limited Michael Turner to 42 yards on 19 carries, spoiling his first opportunity to make amends for a disappointing 2009 season. They rendered Matt Ryan mostly ineffective; he finished with a passer rating of 67.6. Polamalu made an interception late in the fourth quarter to punctuate another smothering masterpiece for a unit guided by defensive coordinator and newly minted Hall-of-Famer Dick LeBeau.
Yet, for all of the defense's best efforts, the Steelers still needed an extra period to beat the Falcons. The likelihood is that the balance of Roethlisberger-less games will follow a similar pattern. With Big Ben, Pittsburgh's offense can be highly explosive. Without him, its production amounts to a field-goal fest ... until, as was the case in OT Sunday, there's a sudden break like Mendenhall's 50-yard touchdown sprint to win the game.
That's OK with the Steelers' defenders, as long as the outcome is the same as it was Sunday.
"We're just trying to go out and make it easier for Dennis," linebacker Lawrence Timmons said. "We're just pretty much playing off each other. That's what makes us a great defense. Nobody's trying to do more than they're supposed to do. Everybody's just doing their job."
Such discipline is likely to never be more important than it will Sunday, when the Steelers face Titans running back and reigning NFL Offensive Player of the Year Chris Johnson. Johnson's incredible speed and elusiveness make him a defensive nightmare because his ability can make the most-thoughtful game plans worthless.
The Titans also are extremely persistent with their use of him. Of Johnson's first 12 carries in the season-opening rout of the Oakland Raiders, six went for one yard or less. He eventually sprang loose for a 76-yard score, and finished the day with 142 rushing yards and two touchdowns.
"He's one of the best athletes we're going to face this whole season," Farrior said. "He's definitely a burner; he's got wheels. He can go inside, come back outside and he'll break down any angle that you have. It's going to be up to us to play good, sound, gap-football defense. Everybody's going to have to know their responsibility and read their keys. Everybody's going to have to play 'hustle defense.' Everybody's going to have to run to the football in order to contain this guy."
Unlike many of Tennessee's opponents, the Steelers actually have done that. Since 2007, only three rushers have gained 100 yards against them, and Johnson isn't one of them. As a rookie in 2008, he had 69 yards on 16 carries in a 31-14 win against Pittsburgh. Last year, he had 57 yards on 15 attempts in a 13-10, season-opening loss to the Steelers.
Of course, since the last time the Steelers saw Johnson, he has put together 12 consecutive 100-yard games and has averaged 140 yards per game during that stretch. Oh, yes, and he's a pretty good pass-catcher as well. The Steelers are expected to have Timmons shadow Johnson in passing situations.
"He can take it to the house any time he gets the ball, and he's even more dangerous when he's catching the ball out of the backfield," Timmons said. "We've definitely got our hands full."
The chore doesn't end with Johnson, however. Quarterback Vince Young presents an additional challenge with his running, as well as his improved throwing.
"Having an athletic, mobile quarterback like Vince is definitely going to give us some problems," Farrior said. "He's going to give us a whole different look than what Matt Ryan did. He's not going to sit back there and be a target in the pocket. He's definitely playing at a high level right now."
As important as it is for the Steelers to successfully navigate their first four Roethlisberger-less games, it is even more crucial, Timmons pointed out, for them not to forget that 12 other games remain. Winning all, or most, of the first four (after Tennessee, the Steelers are at Tampa Bay and home against Baltimore) would contribute greatly to the goal of making another Super Bowl run.
But that could easily be undermined by a poor showing through the remainder of the schedule. The slate of games after Roethlisberger's return hardly have the makings of a prolonged picnic: Home against Cleveland, at Miami, at New Orleans, at Cincinnati, and home against New England.
"We're trying to win a lot of games here," Timmons said. "We're not basing it on a four-game period for our season (to be successful)."