SPARTANBURG -- Leaving the lunch room during another two-a-day session at training camp, second-year Panthers defensive back Captain Munnerlyn has a backpack strapped across his shoulders.

It's not the only thing the former South Carolina Gamecock carries with him.

He also carries a chip on his shoulder.

"That's always been a part of my game, being a small guy," Munnerlyn says during a break between practices.

"They say small corners can't play. That's always been a part of it. He's too small. He's too short. People have always doubted me."

Small by NFL standards -- Munnerlyn is listed at 5-8 and 186 pounds -- he made a big impact as a rookie last season. A seventh-round pick (216th overall), Munnerlyn latched on early and became the team's primary nickel back and primary punt return man.

Munnerlyn wound up starting four games, playing in 15, and making 43 tackles, forcing one fumble and recovering another. He did a solid job returning punts, averaging nine yards per return.

While not eye-popping statistics, Munnerlyn's contribution exceeded the Panthers' expectations.

"He was an extremely pleasant surprise," general manager Marty Hurney says.

Now comes the next step for

Munnerlyn. He is expanding his responsibilities, learning not just to play a man on the corner but to cover slot receivers inside. When Richard Marshall missed offseason work, Munnerlyn stepped into his role and began the next step in his professional evolution.

"With a year under his belt, he looks like he's taken the next step," Hurney says. "He has great instincts and very good cover skills."

Munnerlyn, who got his first name from his great grandfather, has a perpetual energy about him. At South Carolina, his name seemed to be called constantly on the public address system at Williams-Brice Stadium.

He arrived with the Panthers at the same time as defensive coordinator Ron Meeks, who began reshaping the unit last season. The Panthers ranked eighth in yards allowed and ninth in points allowed in 2009.

For Munnerlyn, like the defense as a whole, this season is about building what began last season.

"For me, it's all about learning what other people do," he says. "I'm trying to learn as much as I can. I've got to learn it all.

"They've got me all over the place. Last year, I just focused on corner. I'm seeing what the NFL is all about -- making changes and learning on the go."

Since his high school days in Mobile, Ala., Munnerlyn has fought the label of being too small. He heard it from his friends, his teammates and his coaches.

And here he is, entering his second NFL season.

"I felt like I belonged from Day One," he says. "At my position, you have to play with a lot of confidence and I've always had that swagger about myself."

When others haven't believed in Munnerlyn, he's rarely run short of confidence, an essential trait for a defensive back.

"And when I prove them wrong," Munnerlyn says, "I just smile about it."