Dropping back to pass, eyes aimed downfield, Pittsburgh's Ben Roethlisberger seems to have radar scanning the area around him.

Without even looking, he knows when defenders are closing in and from which direction. Once he "feels" their presence, Roethlisberger takes off — not sprinting, more like getting out of their way. He buys enough time to complete a pass or simply avoid a sack. Even if someone hits him, he's so big that defenders tend to bounce off.

Green Bay's Aaron Rodgers relies on "feel," too. But when his intuition tells him to get moving, he's looking for somewhere to go.

Swift and agile, Rodgers turns into a running back in the open field. He'll juke would-be tacklers and set up blocks that might spring him for a first down or a touchdown, lunging toward contact if it means gaining that pivotal final yard or two.

When it comes to scrambling, the only similarity between these Super Bowl quarterbacks is that they're very good at how they do it. It's such a big part of their success that the championship could be decided Sunday by which defense does the best job of putting the quarterback on the ground once he gets moving.

"Both defenses have their work cut out for them trying to get to those guys," said John Kuhn, a running back who broke into the NFL taking handoffs from Roethlisberger, but now plays behind Rodgers.

"When defenses get to them, it's not over. They've got to get them to the ground. Against Atlanta, Aaron made like four or five guys miss in the pocket on several different plays. He's phenomenal. He's playing at a high level right now. But with Ben, you can't tackle him. He's a beast back there. I think people underestimate how big and strong he actually is."

Mobile quarterbacks were commonplace in Super Bowls during the 1970s, the heyday of Roger Staubach, Fran Tarkenton, Bob Griese and a young Terry Bradshaw. But since the 1980s, it's hard to find a single matchup that pits a pair of guys who scoot around as well as these two.

The 6-foot-2, 225-pound Rodgers ran for 23.8 yards per game this season, the most among all quarterbacks other than Michael Vick. It's almost double Rodgers' number for 2008, his first season as a full-time starter.

That's an interesting change because as quarterbacks mature and get more comfortable, they tend to understand the intricacies of the passing game more and settle into the pocket. They no longer have "happy feet."

Rodgers runs about as often as he did in '08. The spike in production shows that he's become a smarter runner. Another improvement is understanding how to use his feet to avoid sacks. He took 50 last season, 31 this season.

"I think I've done a better job over the last season of knowing when to get out and when to hang in there," Rodgers said. "Now, when you're playing a team like Pittsburgh, I think your reactions have to be on point, your decision-making needs to be quick and instinctive. But every time I see an opportunity to extend the play and get outside the pocket, that's definitely what I'm going to look for."

Against top-seeded Atlanta, Rodgers dropped back, zigzagged up the middle, pump faked and dove into the end zone for a touchdown that put Green Bay up 35-14 midway through the third quarter. In the NFC championship against Chicago, he ran seven times, picking up four first downs, including the touchdown that put the Packers ahead 7-0 on their way to a 21-14 victory.

"He's like a very good scorer in basketball — you know he's going to get points," Steelers defensive coordinator Dick LeBeau said. "From a defensive standpoint, you've got to keep him from controlling the game and monopolizing the game. That's what we have to try and do with Rodgers. He's a great player. He can create, improvise with his feet, go to his second and third choice in the route because he has such a quick release."

The 6-foot-5, 241-pound Roethlisberger isn't as speedy as Rodgers or Vick nor as statuesque as Tom Brady and Peyton Manning; he just makes it work.

This season, 15 of his 34 rushes produced first downs, a rate of 44 percent that was best in the league among quarterbacks who ran more than five times.

"Even if you took the number and name off his jersey, you could watch the film and still know it's Ben," said his backup, Byron Leftwich. "It's never going to be pretty. If you watch his college films, he was making the same kind of plays. I'm quite sure he was doing it in high school and junior high. That's just the type of player he is. It allows him to win a lot of games."

It turns out the formula for slowing scrambling quarterbacks starts with good tackling.

"You've got to come in under control," Steelers nose tackle Casey Hampton said. "If you are out of control, he's going to slip you and get away."

A single player probably isn't enough, either.

"Once you see one guy going back there, you can't just assume he's going to bring him down," Packers defensive end Cullen Jenkins said. "You've got to try to bring in other guys to help."