From obscurity to stardom, NFL underdogs prove doubters wrong

They are future Hall of Famers and key playmakers. Their heroics on the field sent their teams to the Super Bowl.

These superstars all have one thing in common: In the beginning, no one was convinced they could cut it in the NFL, CBS News' Jan Crawford reports.

Patriots fullback James Develin, who scored a touchdown in the AFC championship game, was completely ignored by NFL teams after college. For him, that was motivation.

"That's part of the game, is trying to prove your doubters wrong, trying to play with a chip on your shoulder," Develin said.

Undrafted, the Patriots finally signed him to the practice squad.

Develin took the opportunity and ran with it.

His story is more common than you can imagine, especially with the two teams that will square off on Sunday.

In Seattle's dramatic victory over Green Bay, undrafted players made some of the Seahawks' most pivotal plays, including Jermaine Kearse with the game-winning touchdown.

"You can't measure the heart of a player or the determination or the motivation of the player. You can't grade that," the wide receiver said when asked what part of him got overlooked in the draft. And those stars who were drafted started at the bottom of the heap.

Considered slow and skinny out of Michigan, future Hall of Famer Tom Brady was the 199th pick in the 2000 draft.

Six quarterbacks, some you've never heard of, went ahead of him.

That memory, which Brady discussed in a documentary 11 years later, was hard to take.

"It was just a tough day, you know. I just remember being there with my mom and dad -- sorry about that," an emotional Brady said in the film.

That's a feeling four-time Pro-Bowler Arian Foster, undrafted in 2009, knows well.

"I had my pillow. I was crying ... because this is a dream of yours since I was 7 years old," Foster said. Coming out of the University of Tennessee, Foster also was considered small and slow. After the draft, the Houston Texans gave him a shot on their practice squad.

Two seasons later, Foster was the leading rusher in the league.

"I'm not the biggest. I'm not the fastest. I'm not the strongest running back in the NFL, but I work extremely hard, which is why I've lasted so many years and why I'm in the upper echelon of running backs in the NFL. 'Cause I work my ass off, excuse my language," Foster said.

CBS News asked Brady what makes the difference.

"You know everyone has a lot of hope and a lot of promise when they start their career, but it's also, you gotta earn it. It's a big commitment that it takes to do that," Brady said.

NFL teams spend millions on scouting, evaluating players, going over stats, size and speed.

But they often get it wrong.

"You always have a tendency to choose talent over everything," said Pat Ruel, assistant offensive line coach for the Seahawks. "And this is where you have to be careful because sometimes the best talent will also be the biggest mistake."

"The first thing that defines everybody is talent. And then after talent you're looking for that magic piece of that guy's heart that makes them different," Ruel said.

Sometimes teams don't immediately know how right they were.

In 2011, the Seahawks used the 154th pick in the draft to select an unheralded player out of Stanford.

Two years later, Richard Sherman was leading the NFL in interceptions.

For all these overlooked, under-appreciated players, rejection drove them to prove their doubters wrong.

They knew they had game.

"I believed it 100 percent, and there were still people telling me that I couldn't do it. And I just wanted to prove them wrong. And you know what I did? I did," Foster said.