I walk off the practice field with Carolina Panthers fullback Mike Tolbert. I tell Tolbert, who is listed at 5-9 and 245 pounds, he’s shorter and thicker than I expected.

I try to make it sound like a compliment.

Panthers coach Ron Rivera was San Diego’s defensive coordinator when the Chargers signed Tolbert as a free agent out of Coastal Carolina in 2008.

What was your first impression?

“Honestly, I thought he was roly poly,” says Panthers coach Ron Rivera.

Rivera fails to suppress a smile.

“Oh, he’s going to kill me for that,” Rivera says.

A roly poly is a squat round terrestrial crustacean that, as bugs go, is likeable. It can turn into a ball.

Tolbert only looks as if he could.

Do people underestimate you?

“It happens all the time,” Tolbert, 26, says.

He made the Douglas County High varsity football team (in Douglasville, Ga., about 20 miles west of Atlanta) as a freshman.

Says Tolbert: “People were, ‘Oh, we got him, we got him, he’s a fat running back.’ I got the ball and started moving and it was, ‘Oh, snap. I got my work cut out for me.’ It’s one of those things that definitely catches people off guard.”

He caught the Miami Dolphins last week for a 13-yard run and a short reception for 14 yards. His first step and change of direction are remarkable, and it’s not as if defenders celebrate when they see him lower a shoulder.

“He has athleticism for his size,” says Rivera. “He’s a gregarious personality, outgoing and fun-loving and a hard worker committed to his game.”

Tolbert played fullback at Coast Carolina. Fullbacks rarely are drafted, and Tolbert didn’t expect to be. He signed with San Diego as a free agent.

Says Tolbert: “At first everybody was like, ‘Who the hell is Coastal Carolina?’ So I had to put my school on the map. And then once I got in a game everybody was like, ‘Whoa, this kid’s for real.’ ”

He quickly became a special team’s star and then a back-up tailback and fullback. He played four seasons for the Chargers. He scored 26 touchdowns and three times rushed for more than 100 yards in a game.

San Diego offered him more money than Carolina did. But he signed with the Panthers in March.

“I think it’s a combination of things,” Tolbert says, cleats clicking off the sidewalk behind Bank of America Stadium.

The proximity to Georgia and Coastal Carolina were a factor. So was the presence of Rivera and offensive coordinator Rob Chudzinski, whom he enjoyed playing for in San Diego.

“But at the same time it’s just something different,” says Tolbert. “Change makes you who you are. So do something different.”

One difference: in Carolina, he starts.

Says Tolbert: “It’s to be able to say, ‘You know what? I’m a starter. I play football in the NFL and I’m a starting fullback.’ I mean, what else can you dream of?”

Well, he might dream of joining tailbacks DeAngelo Williams and Jonathan Stewart, who leave practice with the other backs while Tolbert stays late to work on punt protection. That’s him blocking defensive ends.

What are you doing out there with all those big mean guys?

“The coaches asked me to,” Tolbert says.

He plays on four special teams: punt and punt return, kick and kick return. And he still has enough energy to dance on the sideline. You saw him do the Wobble, a line dance, during the Miami game.

“He’s a great athlete,” says tackle Jordan Gross. “He’s big and heavy and he moves like crazy and he’s doing that Wobble whatever on the sidelines.”

Special team specialists are thrilled when they’re joined by an accomplished starter who appreciates what they do and wants to be part of it.

“You see the way he plays offense,” says long snapper J.J. Jansen. “Give him the ball, he’s lead blocker, he catches passes out of the backfield, and that translates to punt teams. He’s capable of taking on a 280-pound defensive end trying to work his d-line moves in open space. What he does is just invaluable.”

Tolbert was never a pure running back. He grew up a defensive tackle, offensive guard and linebacker. He played linebacker as well as running back in high school and was willing to play linebacker at Coastal Carolina.

Linebacker is a lifestyle and Tolbert is still living it. One game the Chargers were so depleted at linebacker Rivera told Tolbert he might have to fill in. Tolbert said he was ready. Rivera was kidding. Tolbert was not.

Tolbert still wants to play.

Can he? Let’s ask Panthers linebacker James Anderson, who last season set a team record with 174 tackles.

No, says Anderson.

Would pass coverage be too much for him?

That’s not it, says Anderson. It’s this. You have to be special to play defense. Tolbert is special on offense, says Anderson. But he’s not special enough to play defense.

Well, could you play fullback?

“Of course,” says Anderson.

Why?

Defensive players are special, he says.

Somebody tells Tolbert about the conversation.

“What did Anderson say?” Tolbert asks excitedly.

He said you can’t.

Aw.

See? Even teammates underestimate Tolbert.

There’s one quality nobody should underestimate, and that’s Tolbert’s passion for the game. The more positions he plays, the more he’s on the field.

Yes, you notice his unconventional body.

But once the newness wears off you notice the joy he brings to whatever task he’s assigned.

“Everybody’s been playing football since they were kids and it’s only a select few of us that get to play as professionals,” Tolbert says as we stand outside the stadium. “So why make it a job when you can have fun like we used have on Saturday mornings with our buddies? That’s what I’m doing here. Getting paid is a bonus.”

Last questions: Could you play linebacker for the Panthers? Tolbert’s face changes. This must be the look upperclassmen saw at Douglas County high.

“Absolutely,” he says. “Absolutely.”