By Adam Hoge-

HALAS HALL (CBS) Rookie linebacker Jon Bostic has made quite a first impression.

In two preseason games, he’s delivered an interception for a touchdown and arguably the biggest hit in the NFL this month.

But he’s also been inconsistent in pass coverage.

“It was a mixed bag,” defensive coordinator Mel Tucker said about Bostic’s performance in last Thursday’s game against the Chargers. “He did some good things and he did some bad things too.”

And yet the Bears might have to start their second-round pick at middle linebacker when the season starts Sept. 8. There are exactly 20 days until the opener and head coach Marc Trestman said he hopes D.J. Williams — who was signed in the offseason to be the team’s starting middle linebacker — can return to practice in the next 12-14 days. That would put him on the practice field when the first game-week starts, but Williams would only have a few practices to get back in shape and get used to a defense he didn’t play in last year.

“We’re getting closer to the season and his conditioning now becomes an issue,” Trestman said. “We think that eventually he’ll be back, certainly. We just don’t know when. It’s just an improving situation. He’s on schedule to come back over the time period that we expected him to.”

But that time period makes it extremely tough to get Williams on the field to play the Bengals Sept. 8. He hasn’t practiced since suffering the calf injury July 31 — an injury that hasn’t allowed him to stay conditioned.

The good news is that Bostic looks like he has the potential to be a very good linebacker in the NFL, but there’s also a lot of evidence indicating that the Bears are going to have to live with some rookie mistakes.

“I’m nowhere near where I want to be and nowhere near where I need to be,” Bostic said Monday. “And it’s about being able to go out there and put this uniform on opening day and I still got a lot of work to do.”

Bostic said Williams has helped in his development during camp and Tucker also lauded the veteran linebacker for contributing in meetings.

“He asks good questions and he’s really smart,” Tucker said. “He has good perspective and can help explain things to younger guys, so he’s very helpful in that regard.”

Unfortunately it’s sounds like the meeting room is the only place Williams will be contributing for at least the next week and a half.

And if that the case, Bostic will likely be the one contributing on the field Week 1 against the Bengals. The Bears might not have any other choice.

Adam Hoge covers the Bears for and is a frequent contributor to 670 The Score. Follow him on Twitter at @AdamHoge.

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