By Chris Emma–

LAKE FOREST, Ill. (CBS) — Motivation comes in many forms for NFL players.

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Perhaps it’s a seminal moment in a career that brings that constant drive or maybe it’s just the will to be great. In a league that requires physical and emotional toughness, inspiration comes in countless forms.

Bears inside linebackers Danny Trevathan and Jerrell Freeman know well what motivates them. It’s that chip on their shoulder. Trevathan was a sixth-round pick out of Kentucky in 2012, while Freeman finally broke into the league that same year after going from Division-III Mary Hardin-Baylor to the Canadian Football League to the Colts.

For the Bears’ two new free-agent prizes, motivation knows no bounds.

“We come from hungry backgrounds,” Trevathan said. “We’re out here to eat.”

Looking to upgrade Vic Fangio’s defense, the Bears made Trevathan the top priority of their offseason. He signed to a four-year deal on the first day of free agency, rejoining coach John Fox, the man who first gave him a chance in Denver.

Freeman followed two days later, signing a three-year deal to play alongside Trevathan.

“He’s just a guy that can do it all,” Freeman said of Trevathan.

Well before he was a Chicago Bear, Freeman was a Saskatchewan Roughrider. His chance with the Tennessee Titans in 2008 didn’t last long — with a cut coming in camp — and he was forced to Canada. Freeman then got a shot with the Colts in 2012 and recorded a franchise-record 145 tackles in his rookie season.

Now 30 years old and established in the league, Freeman never gets complacent. What’s his mentality?

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“I’m a rookie free agent,” Freeman responded.

The demeanor of Trevathan and Freeman has spread throughout the Bears defense. They’re both tremendous talents, combining for more than 16 tackles a game in their collective 89 starts, but that intensity they bring to the practice field can’t be truly measured.

Fangio was looking for players to foster that new defensive identity, and he believes he has two ideal fits to pave the way.

“The attitude just has to spread like wildfire,” Trevathan said. “These guys got to be hungry, and they are.

“When we’re out here, we’re all working for one common goal. That’s to be great and to win a championship.”

During Fox’s first season as Bears coach, the team started five different players at inside linebacker, with Shea McClellin and Christian Jones as the intended starters. Now, they have one of the best inside linebacker pairings in all of football. The Panthers’ tandem of Luke Keuchly and Thomas Davis own the case as the NFL’s best, but Trevathan and Freeman rank near the top.

Knowing their hunger to be great, Trevathan and Freeman would take umbrage to being considered second-best to anyone.

There’s never a lack of motivation for the Bears’ new linebacking tandem.

“That chip,” Freeman said, “never leaves your shoulder.”

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Chris Emma covers the Bears, Chicago’s sports scene and more for CBSChicago.com. Follow him on Twitter @CEmma670 and like his Facebook page.