By Chris Emma–

BOURBONNAIS, Ill. (CBS) — This isn’t Jared Allen’s first rodeo.

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Training camp at Olivet Nazarene is the 12th one for the 33-year-old active leader in sacks, now a converted linebacker for the Bears.

“After 12 years, this still sucks,” Allen joked about training camp.

But this camp is different for Allen, who’s working on a fresh start in Chicago and adjusting to a new 3-4 defense and position.

Rather than rushing out of a defensive end position, Allen’s now working at outside linebacker, where he must adjust to the offense and either come off the edge or drop into coverage.

“At some point, you can’t let it get too big,” Allen said. “It’s still football. I’m just lining up in a slightly different spot and got slightly different responsibilities.”

Such an upbeat mindset has carried the rejuvenated Allen through his first week of this camp.

In just a few practices, Allen has looked improved at the linebacker spot, showing greater comfort in his assignments and more precise steps in coverage. It’s becoming more natural, little by little — something he even acknowledged.

“Every day, learning new nuances throughout,” Allen said. “I think that’s the biggest thing — picking up on how to play different concepts and relate to route structures. Every day I’m getting a little more comfortable.

“The game is about reacting to what you see. The faster you process information, the faster you can react.”

But for Allen, the goal this season was to once again enjoy football. The misery of a 5-11 season in 2014 took a toll on the veteran. This time around, with a new regime and change at his position, Allen has vowed to have more fun.

“Absolutely having fun, 100 percent,” Allen said. “It’s been a blast. The energy around here is high, it’s competitive, it’s uplifting.

“I’m having as much fun as you can possibly have at training camp.”

Ratliff drawing plenty of praise

The centerpiece of a good 3-4 defense is the nose tackle. Each unit needs a big body to line against the center’s facemask and take on the double teams.

In forming a new defensive identity under coordinator Vic Fangio, the Bears just happen to have an ideal fit at the nose tackle spot. Jeremiah Ratliff was brought in by Phil Emery late in the 2013 season to add depth. The natural 3-4 nose tackle was stuck working in a 4-3 system previously.

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Now, the 33-year-old Ratliff is making a statement early in Bears camp.

“Jeremiah Ratliff is the final boss you got to face at the end of a video game,” said Bears guard Kyle Long, who’s seen a lot of Ratliff in the trenches.

Added center Will Montgomery: “The guy is a stud.”

Ratliff, the 6-foot-4, 303-pound lineman, had his best years in Dallas, and he’s trying to re-create those in Chicago amid a transition.

Of course, the key for Ratliff is staying healthy. His last full 16-game season was 2011, and he has played just 22 games since that point.

In the Bears’ physical practices, few have been as tenacious as Ratliff.

“I’ve been very impressed,” Bears coach John Fox said. “With any veteran player or any time you come in as a new coach, you file things you hear, reps, all that stuff, but you really formulate your own opinion. He’s been a good performer for us thus far.”

Fuller feeling poised in second season

There’s been a lot of focus on recent Bears first-round picks in training camp. Shea McClellin has impressed at linebacker, Long is a leader for this team and Kevin White is missing practice with shin splints.

Meanwhile, cornerback Kyle Fuller, the Bears’ first-round pick of 2014, is quietly going about his business.

“A lot of things are second nature,” Fuller said. “You can focus on specific things and not worry about things, because you know what’s going on.”

A 23-year-old Virginia Tech product, Fuller played in all 16 games last season, recording 64 tackles, breaking up 10 passes and recording four interceptions.

There were downs to the ups, too, but Fuller showed the promise that the Bears need at cornerback.

Fuller was drafted to eventually replace Charles Tillman, and that came sooner than expected when Tillman was lost for the season due to injury in 2014. Now, Tillman is off in Carolina, and Fuller is filling the void.

“Just having that year under my belt and knowing what to expect,” Fuller said, “it makes things go a little bit smoother.”

Extra points: Tackle Michael Ola was diagnosed with a knee strain after his Wednesday injury … Tackle Tayo Fabuluje suffered an asthma attack for a second straight practice … The Bears will practice on Saturday at Soldier Field in a 36-play scrimmage.

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Follow Chris on Twitter @CEmma670.