It didn't take long for Datone Jones to become acquainted with the two sides of Julius Peppers.
There's the soft-spoken version of the eight-time Pro Bowler prevalent in social and off-the-field situations. There's also the 6-foot-7, 290-pound alpha male fuming with white-hot intensity whenever he steps onto a football field.
Green Bay Packers defensive lineman Mike Daniels said earlier this season that that's when Peppers "turns into a raging psychopath."
Jones, a second-year defensive end, began playing football right around the time Peppers was drafted into the NFL in 2002. When he was young, Jones always hoped he'd have the chance to play with the likes of Ray Lewis, Brian Urlacher, Brett Favre or Peppers.
Then, Jones heard the 13th-year veteran bark on the practice field.
"He's intense. Words can't even explain it," Jones said. "The first I heard him be like, 'Let's go.' I'm like, 'Holy snap, who is this dude?' You expect that when you first meet him on the practice field the first day, but then he's really humble, quiet and feeling everything out.
"Game day comes, I get a head butt behind my helmet and get whiplash."
The Packers believe this is the kind of leader they needed. For years, Ryan Pickett was a father figure on the defensive side of the ball. Last fall, Johnny Jolly's return from a three-year NFL suspension energized the locker room early on.
Peppers emits a different kind of leadership. He's not a social butterfly, but his words carry weight. When Peppers speaks, which isn't often, everyone in the room listens.
His credentials are unmatched. Peppers has the third-most sacks among active NFL players (1191/2). His strip sack in Sunday's 19-7 loss over Detroit ensured he'll have at least one forced fumble in each of his 13 NFL seasons.
Still, Peppers doesn't enjoy basking in the accolades. He flew into Green Bay under the cover of darkness in March and was gone by the time his three-year, $27 million deal was announced. No elaborate news conference. No ticker-tape parade.
He's all business.
"Julius, he's a man of few words but he has some wisdom tucked away in there," outside linebacker Clay Matthews said. "It's always great to pick his brain, kind of see where he's at and what he feels about certain situations.
"It's great having a guy not only of his caliber but of his tenure in this league to kind of reach out to him and see what's going on with him."
Peppers has made a big impact with a young collection of defenders. He's assigned to the outside linebackers room in meetings, but he's been open to imparting advice to the defensive line, as well.
Jones has taken a lot from him. The 2013 first-round pick had three sacks his rookie season, but remembers frequently getting hung up on offensive linemen when his first move failed.
Every practice has been a lesson with Peppers. Jones likens it to wanting to "impress somebody" when you're a child. Nobody ever wants to mess up in front of the popular kid.
"He always has a counter for everything," said Jones, who has matched his 2013 output with 10 tackles in three games this season. "When I first got here as a rookie, I'd beat a guy but I wouldn't have a counter move, so when I lost on the first move I'd be dead. Now I've developed a counter move and so far this season, you've been able to see me really affect the quarterback."
On Sunday, Peppers will make his first appearance at Soldier Field facing the Chicago Bears team that released him last March. When asked about it earlier this weekend, Peppers was adamant it's just another game.
A quick glance at his body language, and you tend to believe him.
The Packers don't care about Peppers' bedside manner, though. What concerns them is his on-field production. After a slow start, Peppers is starting to become a central figure in the reworked defense.
According to Pro Football Focus, he leads the defense with 11 pressures (one sack, four quarterback hits and six hurries). He's helped the Packers boost their average quarterback hits per game from 2.0 a year ago to 3.7 this season.
Defensive coordinator Dom Capers believes Peppers' presence has helped generate more pressure with a four-man rush, an area in which they struggled in 2013 despite tying for eighth in the NFL in sacks.
"Since he's been here, the great thing is he's not missed one practice, he's been in every meeting," Capers said. "Julius is a man of few words, but he's very smart and he pays attention. I think he's been a really positive influence on our younger players."
Capers calls it the "society of productivity." As a coach, he can talk until his voice grows hoarse about the virtues of fundamentals. When players see someone as successful as Peppers, it's only natural to buy in.
Peppers might not show it, but the importance of this season hasn't been lost on him, either. The Bears released him to avoid his $20 million cap number, but it begged the question about a 34-year-old's place in a young man's game.
Many of his All-Pro classmates from the 2002 NFL draft like Ed Reed, Clinton Portis and Jeremy Shockey are out of football. Only a few remain.
Tramon Williams believes Peppers still has plenty to give. After last January's playoff loss to San Francisco, the 31-year-old cornerback made a plea for general manager Ted Thompson to bring in more veterans to augment a young roster.
It's early, but the Packers have seen the move pay dividends.
"He's just a complete player," Williams said. "I don't think there are many guys out there who can do what he do, even at the age of 34. I can still look at him and think he's better than most guys in this league, at that age. He's just a freak of nature. He brings everything to the table."
— firstname.lastname@example.org and follow him on Twitter @WesHod