LAKE FOREST, Ill. -- Jonathan Bostic assumes the starting role at middle linebacker in the aftermath of news D.J. Williams is out for the season with a torn pectoral tendon, and the Chicago Bears expect the rookie to build on the excitement he generated throughout the preseason.

Subbing for Williams as the starter in the middle for most of training camp, Bostic collected 13 tackles in the preseason, and returned an interception 51 yards for a touchdown in the exhibition opener at Carolina to create anticipation for the linebacker’s debut as a full-time starter among observers.

“Of course we’re going to miss D.J. (Williams) a lot,” cornerback Tim Jennings said. “But I’m excited about Bostic. I know he put on a show this preseason. I know a lot of guys are excited about Bostic to see what he’s going to be doing. Of course, you don’t want D.J. to go down like that and miss the rest of the year, but this is just an opportunity for Bostic to let everybody know he’s here for a reason.”

Drafted in the second round out of Florida, Bostic filled in for Williams late in the third quarter of the team’s win last Thursday over the New York Giants and played the final 21 snaps. Bostic received credit for one assisted tackle in the victory, but for the most part struggled, grading among the worst of the team’s defenders.

Jonathan Bostic proved to be a playmaker in the preseason and will now help fill the spot vacated by an injured D.J. Williams. David Banks/USA TODAY Sports

But that was to be expected with Bostic coming into the game cold.

“You always hear ‘next man up, anything can happen,’ but the situation that happened like that, it’s kind of like, ‘Man, these things really do happen,’” Bostic said. "I wasn’t too surprised about it. Now I’ve got to kind of step up now. I don’t want any drop offs to me from D.J. Really, (I’ve) just got to go out there and just prepare the best I can and go out there and do my best. I did alright (against the Giants); a lot of stuff still to clean up. Especially getting thrown in there kind of like that, I really wasn’t expecting it. But you’ve got to be expecting it. (I’m) just learning from those mistakes I made in the game and cleaning those things up and trying not to make the same mistakes twice.”

Bostic spent time during Monday’s practice working at his customary spot in the middle, but also took repetitions at strongside linebacker as a contingency plan for if James Anderson suffered an injury that would force him to miss time. When Anderson sustained a back injury that forced him out last Thursday, the Bears plugged in veteran Blake Costanzo and kept Bostic in the middle.

If that situation takes place again, there’s a chance the Bears would move Costanzo to the middle and Bostic to the strongside.

“He’s ready,” defensive tackle Stephen Paea said of Bostic. “In the preseason, he showed some flash. Everybody’s got to step up.”

But Bears coach Marc Trestman knows that won’t be easy for a rookie, no matter how promising a future he has in the defense.

“He hasn’t spent a lot of time out there, but he has played,” Trestman said. “He doesn’t have the experience that D.J. has, but he has speed and he’s an explosive young man. It’s just about working together with the guys and getting acclimated to the calls, and fits and things like that. I think we’ll do fine.”

To ensure that happens, Bostic said that in addition to taking copious notes during meetings, he’s picked the brains of Lance Briggs, Anderson and Williams. Naturally, Bostic’s grasp of the system is better now than it was during the preseason.

Still, Bostic says there’s a long way to go before he’s exactly where he wants to be.

“I feel more ready each and every day,” Bostic said. “I’m understanding it more, reacting faster. Guys are helping me out. Lance, even D.J., James, they’re watching me, making sure I’m making the calls as well because anything can happen. I’ve got three great linebackers in that meeting room. To learn from them each and every day, like I said before when I first got here, not too many people can walk into a linebacker room, and have the number of years that (fellow rookie linebacker) Khaseem (Greene) and I both were able to walk into. So we’ve been taking full advantage of that.”