The Pittsburgh Steelers realize it could have been a whole lot worse.

Dennis Dixon could have easily thrown another couple of interceptions. The defense could have allowed a single touchdown. Jeff Reed could have missed that 52-yard field goal.

If any one of those had happened, the Steelers might be staring at a possible 1-3 or 0-4 start without suspended quarterback Ben Roethlisberger. Instead, they played just well enough to beat the Atlanta Falcons 15-9 in overtime on Sunday — a victory that told them that, unlike many NFL teams, they're good enough to win with their No. 3 quarterback.

That was one big sigh of relief exhaled by an entire football team after Rashard Mendenhall's 50-yard touchdown run won it.

For more than five months, the Steelers knew they must get by for a month or longer at the start of the season without the quarterback who was good enough to win two Super Bowls in four seasons. They were convinced they had enough left to win without him but, until they actually did it, there was always that lingering doubt.

After all, the Steelers hadn't won a game without Roethlisberger at quarterback since Charlie Batch started and won the 2006 season opener against Miami, a few days after Roethlisberger had an appendectomy.

Now, they might have to win for a couple of weeks without left tackle Max Starks, who has a high ankle sprain in his left leg and seems certain to miss at least one game. Such injuries commonly sideline a player for multiple weeks. He was replaced by former Bills tackle Jonathan Scott.

"We've got some things to work on, absolutely, like all 31 other teams do," coach Mike Tomlin said. "But we get to do it while we're 1-0."

Winning at Tennessee (1-0) on Sunday will be more difficult. Still, the Steelers believe if their defense can keep performing at a 2008-like level, Roethlisberger will be trying not to save the Steelers' season once he returns Oct. 17 against Cleveland, but to keep it going.

"Obviously, we seized the moment," said Dixon, who had a relatively rough start yet still managed the offense well enough to lead four scoring drives.

For this game, it wasn't about who was missing but who was back — safety Troy Polamalu and end Aaron Smith on a defense was No. 5 overall in the league last season but didn't really play up to such a level. There were too many long completions, too many blown leads in the fourth quarter, too many wide receivers who got loose downfield only a season after the Steelers had one of the best years statistically by any NFL defense since the 1970 NFL-AFL merger.

One of the big question marks about these Steelers was how a defense loaded with players who are 30 or older would respond after such a season. Whether a defense that has been one of the NFL's best for years was getting too old and fragile to play at a top-of-the-league level. Whether Polamalu and Smith would hold up after being injured and out much of last season.

For one game, this was the answer: The Falcons moved the ball inside the Steelers 20 on only one of 13 possessions.

"That was a great way for our defense to start," James Farrior said.

This week, that defense will be challenged by Titans running back Chris Johnson, who ran for 142 yards and two touchdowns Sunday in Tennessee's 38-13 victory over Oakland. Johnson is the NFL's leading rusher since the start of the 2008 season, and is the only running back during that time to average more than 100 yards per game (105.5 yards).

However, only the Vikings have allowed fewer yards rushing than the Steelers during that period. Since 2005, the Steelers have given up only four 100-yard games.

"That's a great defense over there," Falcons coach Mike Smith said.