David Cobb took a handoff one morning this week, took two strides to his left and toward the line, then suddenly cut hard to his right. Seemingly before anyone could react, the Gophers' 220-pound back was 10 yards upfield, behind the linebackers and coasting to a jog as whistles blew to end the play.

But before Cobb could enjoy the moment, could revel in his breakaway play, he brushed past secondary coach Jay Sawvel, who reached out and with a flick of his wrist and stripped the ball out of the tailback's arms.

The lesson: Never relax.

"Man, I think that's the first one," Cobb said of his oops moment. "He snuck one in there. But I learned from it -- at all times, ball security. Always."

Both parts of that play illustrate why the Gophers are quietly excited about the sophomore's chances to turn tailback from a question mark to an exclamation point this season. The teenager from Killeen, Texas, possesses a natural ability to find holes and drive through them in a hurry. And he's humble enough to learn from his mistakes.

"When I got here as a freshman, I didn't really understand the [offensive] scheme as well as other players," Cobb said. "As far as talent, everybody has talent. So it really comes down to who understands the plays better, who learns what [coaches] want, who works hardest. That's who gets to play."

The Gophers claim to have no idea yet who will play once the 2012 season starts -- but that doubt is reflection of their strength at the position, they say, not weakness. Cobb joins fellow sophomores Donnell Kirkwood and Devon Wright, transfer student James Gillum, and even a couple of freshmen in a hard-to-predict competition for playing time.

"We don't have one guy," offensive coordinator Matt Limegrover said. "The crazy thing is, sometimes I've got to do a double-check. I'm watching the line and all of a sudden, one of those backs will make a great move and break one, and I'll be like, 'Was that [No.] 27 or 21 or 20 or 4?' And that's a great thing."

It's a great thing for Cobb, who has been a tailback since he was 10 and his father, a longtime Walter Payton fan, encouraged him to switch from playing safety on his youth team.

"I fell in love with it right away. I liked scoring touchdowns, and I liked the contact, so it's fun," Cobb said. "As a running back, you have to learn how to take care of your body, really hit the weight room hard. It's not an easy decision, but it's fun. There's nothing like playing football."

His chance to play this fall might be more secure had Cobb not torn a ligament in his right knee last season. He received extensive playing time in only one game, the Gophers' blowout loss at Michigan, but he picked up 54 yards on only eight carries. The knee injury wasn't particularly serious, but it came too late in the season for Cobb to build on that performance.

"I felt like I was really starting to gel with the offense," Cobb said. "To get familiar with the plays, get a chance, and then have an injury like that, all you can really do is sit back, encourage the other guys and learn from it. I know you just have to keep proving yourself."

The Gophers weren't sure he understood that a few months ago. Limegrover said the coaching staff sensed "a sense of entitlement" in Cobb during spring practices, like "he thought 'OK, I'm going to be in the mix just because I played a little bit as a freshman.' But it was kind of an eye-opener for him in the spring," Limegrover said. "Hey, there's a good crop of guys here, and everyone is getting better and better. So it was a wake-up call."

Cobb woke up and realized, Limegrover said, that his 3,000-yard high school career, his 35 career touchdowns, didn't mean much now. "He's come out here with a very good demeanor," Limegrover said. "He's been really sharp and really on top of things from an assignment standpoint, which tells me he's locked in pretty well."