Bears ready to ring in new era of defense

The Bears will take the field Thursday night at Soldier Field looking completely different.

Of course, that’s the point. So disgusted was Bears chairman George McCaskey that he fired GM Phil Emery and coach Marc Trestman in December, the day after their 5-11 season ended.

He hired GM Ryan Pace, who has brought in 30 new football operations department staffers alone. New head coach John Fox retained only two assistants from the previous season, keeping only one — receivers coach Mike Groh — in his same role.

Pro Bowlers Charles Tillman, Lance Briggs and Brandon Marshall are gone.

More than half the Bears’ 90-man roster is new this season; only four Opening Day defensive starters from last year — Jared Allen, Shea McClellin, Tim Jennings and Jeremiah Ratliff — are expected to start against the Dolphins.

Nowhere will the Bears’ philosophy change be more apparent than when the Dolphins have the ball. Gone is the Lovie Smith Tampa 2 defense that Mel Tucker couldn’t replicate, replaced by Vic Fangio’s aggressive 3-4 front.

To get to know the Bears’ new defense, you have to understand how Bears’ coaches explain the rationale behind it:

• A game day ‘master.’ Defensive backs coach Ed Donatell, who worked with Fangio the previous four seasons in San Francisco, described the coordinator as “a master game caller.” His exotic blitzes are the opposite of the Bears’ risk-averse defenses of the past two years.

Last season, his 49ers were the third most productive team when they blitzed, according to Pro Football Focus.

“This guy has a lot of chess moves in him,” he said. “He can help players — and nobody knows he’s doing it.”

Pressed to explain, Donatell didn’t want to divulge secrets.

“There are little subtle things,” he said. “But preparation goes into it. It’s not an accident.”

• Pushing ends. The Bears’ two defensive ends are expected to focus more on rush defense than the classic 4-3 pass-rushing end.

“Playing defensive end is all about knock-back, separation and making plays,” defensive line coach Jay Rodgers said. “And then when it gets in passing situations, just being able to get off the ball and get into the pocket.”

The team figures to use four-man fronts on passing downs.

• Aggressive DBs. Donatell dictates three tenets to his defensive backs.

“We’re gonna protect the ball deep, we’re gonna protect the seams, and we’re going to be a team that goes after the football,” he said.

While the Bears imported 6-2 Alan Ball to compete against the division’s tall receivers, Donatell said could play the 5-8 Jennings outside, rather than in the slot, instead.

“We can play little guys, tall guys, thick guys,” Donatell said. “Anybody that wants to compete can be part of it.”

• Calculating linebackers. Perhaps the biggest challenge for new inside Christian Jones is and McClellin is understanding pass route concepts based off the formations and personnel that teams use.

“And then it just has to click-click-click,” inside linebackers coach Glenn Pires said. “You have to be thinking so much more before the snap. That’s going to be the key. If you wait until the ball is snapped — not gonna happen.”

That applies to outside linebackers, too. While Jared Allen, Lamarr Houston and Willie Young, will play pass coverage occasionally, their pre-snap responsibilities are still similar to when they were 4-3 ends.

“It’s no different when you’re walked out of the box as an outside ‘backer,” outside linebackers coach Clint Hurtt said. “You want to see the splits of the receivers, know formation tendencies and things like that.”

• A new enthusiasm. Players are practically giddy to be playing in Fangio’s new, aggressive defense. And while the excitement will be palpable Thursday night, the coordinator knows it doesn’t mean much in mid-August.

“Like I tell the defense in meetings, it’s easy to be enthusiastic and emotional and physical early on,” Fangio said. “You’ve got to maintain it over a 16-game schedule —through a potential bad performance, through a potential bad day. You’ve got to just keep grinding.”

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Email: pfinley@suntimes.com