A quarter of the way into the season, Sun-Times expert Adam L. Jahns examines the 3-1 Bears as they head out of their bye week:

The Bears’ identity after four games is …

The Bears’ defense looks special, and Khalil Mack jerseys are everywhere. But that’s only half of the Bears’ new identity. The other part of it is still developing on offense, with quarterback Mitch Trubisky in his first season with coach Matt Nagy. Trubisky was drafted to change the franchise. The defense is great, but Trubisky is expected to be, too.

Is Mitch Trubisky progressing properly?

It depends on your definition of ‘‘properly’’ and on how patient you are as a person, but Trubisky’s six-touchdown performance against the Bucs should erase some concerns about his abilities. He’s not done making mistakes or looking overwhelmed at times. Good quarterbacks still have bad games. But his progress was obvious.

What kind of head coach has Matt Nagy proved to be?

On the field, Nagy still has much to prove because Trubisky still has much to prove. If anything, Nagy has proved he’s different from his predecessors, John Fox and Marc Trestman. It starts with his demeanor, energy and philosophical direction. Nagy has been a breath of fresh air at Halas Hall.

The most impressive part about Khalil Mack has been …

Everything. It’s his four consecutive games with strip-sacks and his low-key persona in the locker room. For as much attention as Mack demands from opponents on the field, he doesn’t seek any when he’s off it. It’s early in Mack’s run with the Bears, but it’s obvious he’s a special player. Seriously, what was Raiders coach Jon Gruden thinking?

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The Bears’ MVP not named Mack has been …

Defensive lineman Akiem Hicks. He’s performing at an All-Pro level again. He has three sacks and two forced fumbles in four games, despite missing an entire half against the Bucs after being ejected for making contact with an official. The Bears arguably have the best defensive front in the NFL. That starts with Hicks and Mack.

The biggest surprise has been …

Trubisky’s six touchdown passes against the Bucs. With all due respect to Sid Luckman and Jay Cutler, Trubisky’s performance signaled the start of a new era for the organization. Modern football finally arrived in Chicago. A new precedent was set in emphatic, high-scoring fashion.

The biggest disappointment has been …

Is it possible not to have one? The Bears are 3-1, and Trubisky finally had the breakout game to silence his critics. But if we’re nitpicking, running back Jordan Howard has averaged 2.5, 2.5 and 2.3 yards per carry in the Bears’ last three games.

The Bears are on track to …

Be that surprise team in the playoffs. The Bears have a defense that deserves to be in the postseason. Will Trubisky and the offense catch up? I think so. The Bears will play meaningful games in December. It’s OK to be encouraged and excited.