Bears

Bears linebacker Jon Bostic is getting more comfortable learning the defense. (Jonathan Daniel / Getty / August 14, 2014)

Bears linebacker Jon Bostic sensed what was coming. On a third-and-1 play early in the first quarter Thursday at Soldier Field, Bostic noticed Jaguars receiver Allen Hurns motion into "a two-man stack" beside fellow receiver Marqise Lee and his radar went off.

Calling on recent film study to anticipate a crack toss play to running back Toby Gerhart, Bostic quickly alerted defensive end Jared Allen of the read, then waited.

When the snap came, with Jaguars quarterback Chad Henne flipping a toss left to Gerhart, Bostic darted downhill, shed left tackle Luke Joeckel's block and leveled Gerhart for a 4-yard loss.

Sure, that stop forced the Jaguars to settle for a 49-yard Josh Scobee field goal on Thursday's opening possession. But of more importance, it offered invaluable positive reinforcement for a still-green linebacker in a still-developing defense.

"That came from something just watching film," Bostic said. "So you just keep improving, keep learning the game and how this defense works and that's only going to help. … My main thing was play faster. Don't think. Have fun."

It wasn't all fun for the Bears during Thursday's 20-19 exhibition victory over the Jaguars. In fact, a one-sided first quarter offered little fun at all. The Bears were outgained 134-8, running just five plays to the Jaguars' 28. Yet by Friday afternoon, coach Marc Trestman had found an ounce of positive spin on that rough defensive start.

"Good for our conditioning," he said with a straight face.

OK. That's something. But that wasn't all that had Trestman feeling encouraged as the Bears marched toward the penultimate week of the preseason. Trestman's Friday film review revealed numerous bright spots for a defense still feeling its way around in mid-August.

Shea McClellin seemed more at ease in his second exhibition game at linebacker. And a first-unit defensive line that has been active and sturdy throughout training camp continued establishing itself as a stingy bunch against the run.

The Bears surrendered only 25 rushing yards on their first three defensive series, allowing 2.5 yards per carry as Bostic, McClellin and Allen each had tackles for losses.

If McClellin's exhibition debut against the Eagles was shaky — he contributed only two tackles in 29 snaps — he played with more assertiveness against the Jaguars, delivering four stops.

"He was around the ball a little bit more," Trestman said. "He was more active. … You could see a little more confidence, more natural reactions to making plays."

Bostic also admitted feeling added comfort Thursday night as he looks to find his niche. Since the spring, he has spent time rotating between responsibilities at strong-side linebacker and middle linebacker, the latter providing more of a comfort zone. But Trestman has no immediate plans to narrow Bostic's focus to one role.

"It's tough because of his flexibility," Trestman said. "He plays middle (linebacker) very well. … If we lose somebody he can move into either position."

For the defense as a whole, Friday's trip to Seattle to face the Super Bowl champion Seahawks will provide a much more telling progress report. Starters on both teams figure to play into the second half.

And as defensive tackle Stephen Paea said Thursday night, "Seattle's not Jacksonville. So obviously we have a lot of work to do."

But the Bears, Paea promised, also are showing they can be much more vicious on defense than they were a season ago.

"You can feel it up front," Paea said. "On that D-line, there's an energy and a focus on every guy winning every down. And we're developing the ability to read our run-pass keys plus our ability to work on technique and moves to shed blocks."

•The Bears placed tight end Zach Miller on injured reserve with a season-ending foot injury and signed receiver Kofi Hughes to fill the open roster spot.

dwiederer@tribune.com

Twitter @danwiederer