Nebraska football coach Bo Pelini is an aggressive, take-charge sort. 

He has a bit of a mean streak (maybe you've noticed). His confidence is unwavering.

Surprisingly, his defense often fails to show those characteristics.

In one breath, Pelini sounds somewhat resigned about this season's unit. In the next breath, he seems optimistic.

"We're young, obviously," he told me after Saturday's victory against South Dakota State. "We need to get a little better leadership (on defense). You just have to keep finding different ways to push their buttons."

In the absence of overflowing talent, a defense had better possess a killer instinct and at least a couple of forceful leaders. We've seen scant evidence of a killer instinct in Nebraska's 2013 defense. Listening to coaches and players, forceful leadership (think Jason Peter and Grant Wistrom) also may be lacking.

"We need some guys who will step up when things are going bad," said Husker defensive coordinator John Papuchis. "Coaches can motivate and talk. But it helps when players are doing it. It helps when there's true leadership within the group."

Nebraska (3-1) has four team captains, but only one is a defender — senior nickel cornerback Ciante Evans. By his own admission, he had a rough second half as the defense melted down Sept. 14 against UCLA. Also by his own admission, Evans isn't vocal by nature.

Talk is one thing. Leading by example is even better. An excellent leader does both well.

As UCLA reeled off 38 unanswered points, plenty of Nebraska defenders spoke up on the sideline, said Husker sophomore defensive end Randy Gregory.

"But you also have to go out there and perform on the field," he said. "There's only so much you can say."

Classify Gregory as an emerging leader. He still could be crucial in that regard this season. Pelini likes Gregory's maturity and competitive nature. Gregory is willing to speak up, and he's making plays. He has 17 tackles (five for loss), five quarterback hurries and returned an interception for a touchdown Saturday.

Trouble is, Gregory arrived on campus in late July. A transfer from Arizona Western Community College, he hasn't been around long enough to fully establish himself as a go-to leader.

"I know what needs to be done, I know what needs to be said," he said. "I don't really look to anyone else. I think I'm my own leader. I think I'm a leader to some of the guys on the team."

He said he needs to be more vocal.

"I think I'm more vocal than what people expected coming in," he said. "But somebody really has to step up and be the leader of the defense — making plays and speaking up when they need to.

"The more experience I get in the games, the better I'll get at it and the more I can speak up and speak to the coaches more about what's going on in the game."

Corey Cooper would seem a logical candidate to become a defensive leader. The 6-foot-1, 210-pound junior safety is perhaps the team's most physical downhill tackler. He leads the squad with 30 stops. He plays a critical position in the heart of the unit. But he is in only his first season as a full-time starter. He needs more time to establish confidence in himself before he can draw it out of others.

Nebraska's defense won't derive much confidence from watching video of Saturday's game. There were an inordinate number of missed assignments, especially along the line, Pelini said. Once again, poor tackling was an issue.

Nebraska ranks 106th nationally in total defense, allowing 463.8 yards per game — 103 more than its average in 2012.

Defenders must build confidence in practice, then take it into games, Papuchis said. He thinks Nebraska defenders prepared diligently for South Dakota State. But they tend to prepare with a narrow focus, the coach said. If something happens outside the realm of the game plan, it throws the defense off-kilter.

Pelini insists "the potential is there" for substantial improvement. As it stands, he said, the defense is "nowhere near" where it needs to be. The limitations won't be solved overnight.

"If we keep progressing each week, we'll be fine," Pelini said confidently.

It would be easier to believe Pelini if the defense had at least one surefire All-Big Ten pick. Evans and senior corner Stanley Jean-Baptiste, who already have a combined seven interceptions, are probably the closest. Gregory is moving in the right direction.

Can forceful leaders emerge quickly?

"I hope so. I don't know," Papuchis said. "We work really hard at trying to cultivate leadership models in our program. But at the end of the day, you can't make somebody be a leader.

"If the leadership has to come from the coaches, so be it."

Sounds like a challenge. Who will step up?

Reach Steven M. Sipple at 402-473-7440 or ssipple@journalstar.com.